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Kłos J, McCrudden G, Brouard M, Perkins T, Seamons SA, Herráez-Aguilar D, Aoiz FJ. Experimental and theoretical studies of the Xe-OH(A/X) quenching system. J Chem Phys 2018; 149:184301. [PMID: 30441911 DOI: 10.1063/1.5051068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
New multi-reference, global ab initio potential energy surfaces (PESs) are reported for the interaction of Xe atoms with OH radicals in their ground X2Π and excited A2Σ+ states, together with the non-adiabatic couplings between them. The 2A' excited potential features a very deep well at the collinear Xe-OH configuration whose minimum corresponds to the avoided crossing with the 1A' PES. It is therefore expected that, as with collisions of Kr + OH(A), electronic quenching will play a major role in the dynamics, competing favorably with rotational energy transfer within the 2A' state. The surfaces and couplings are used in full three-state surface-hopping trajectory calculations, including roto-electronic couplings, to calculate integral cross sections for electronic quenching and collisional removal. Experimental cross sections, measured using Zeeman quantum beat spectroscopy, are also presented here for comparison with these calculations. Unlike similar previous work on the collisions of OH(A) with Kr, the surface-hopping calculations are only able to account qualitatively for the experimentally observed electronic quenching cross sections, with those calculated being around a factor of two smaller than the experimental ones. However, the predicted total depopulation of the initial rovibrational state of OH(A) (quenching plus rotational energy transfer) agrees well with the experimental results. Possible reasons for the discrepancies are discussed in detail.
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Affiliation(s)
- J Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA
| | - G McCrudden
- The Department of Chemistry, The Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - M Brouard
- The Department of Chemistry, The Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - T Perkins
- The Department of Chemistry, The Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - S A Seamons
- The Department of Chemistry, The Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - D Herráez-Aguilar
- Faculty of Experimental Sciences, Francisco de Vitoria University (UFV), 28223 Pozuelo de Alarcón (Madrid), Spain
| | - F J Aoiz
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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Abstract
We present a new three-dimensional potential energy surface (PES) for the NH(X3Σ-)-He van der Waals system, which explicitly takes into account the NH vibrational motion. The NH-He PES was obtained using the open-shell single- and double-excitation coupled cluster approach with non-iterative perturbational treatment of triple excitations. The augmented correlation-consistent aug-cc-pVXZ (X = Q, 5, 6) basis sets were employed, and the energies obtained were then extrapolated to the complete basis set limit. Using this new PES, we have studied the spectroscopy of the NH-He complex and we have determined a new rotational constant that agrees well with the available experimental data. Collisional excitation of NH(X3Σ-) by He was also studied at the close-coupling level. Calculations of the collisional excitation cross sections of the fine-structure levels of NH by He were performed for energies up to 3500 cm-1, which yield, after thermal average, rate coefficients up to 350 K. The calculated rate coefficients are compared with available experimental measurements at room temperature, and a reasonably good agreement is found between experimental and theoretical data.
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Affiliation(s)
- R Ramachandran
- LOMC-UMR 6294, CNRS-Université du Havre, 25 Rue Philippe Lebon, BP 1123, 76 063 Le Havre Cedex, France
| | - J Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA
| | - F Lique
- LOMC-UMR 6294, CNRS-Université du Havre, 25 Rue Philippe Lebon, BP 1123, 76 063 Le Havre Cedex, France
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Lique F, Kłos J, Le Picard SD. Fine-structure transitions of interstellar atomic sulfur and silicon induced by collisions with helium. Phys Chem Chem Phys 2018; 20:5427-5434. [PMID: 28967011 DOI: 10.1039/c7cp05092e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Atomic sulfur and silicon are important constituents of the interstellar matter and are both used as tracers of the physical conditions in interstellar shocks and outflows. We present an investigation of the spin-orbit (de-)excitation of S(3P) and Si(3P) atoms induced by collisions with helium with the aim to improve the determination of atomic sulfur and silicon abundances in the interstellar medium from S and Si emission spectra. Quantum-mechanical calculations have been performed in order to determine rate coefficients for the fine-structure transitions in the 5-1000 K temperature range. The scattering calculations are based on new highly correlated ab initio potentials. The theoretical results show that the (de-)excitation of Si is much faster than that of S. The rate coefficients deduced from this study are in good agreement with previous experimental and theoretical findings despite some deviations at low temperatures. From the computation of critical densities defined as the ratios between Einstein coefficients and the sum of the relevant collisional de-excitation rate coefficients, we show that local thermodynamic equilibrium conditions are not fulfilled for analyzing S and Si emission spectra observed in the interstellar medium. Hence, the present rate coefficients will be extremely useful for the accurate determination of interstellar atomic sulfur and silicon abundances.
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Affiliation(s)
- F Lique
- LOMC-UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123-76 063 Le Havre cedex, France.
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Dellis D, Samios J, Collet B, Versmold H, Kłos J, Marinakis S. An investigation of thermodynamics, microscopic structure, depolarized Rayleigh scattering, and collision dynamics in Xe-N 2 supercritical mixtures. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.06.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Beutner V, Zhang SG, Meyer H, Kłos J. The near-IR spectrum of NO(X̃ 2Π)-He detected through excitation into the Ã-state continuum: A joint experimental and theoretical study. J Chem Phys 2016; 145:124318. [PMID: 27782644 DOI: 10.1063/1.4963228] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present the first measurement of a bound-state spectrum of the NO-He complex. The recorded spectrum is associated with the first overtone transition of the NO moiety. The IR absorption is detected by exciting the vibrationally excited complex to the Ã-state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. We recorded two bands centered around the NO monomer rotational lines, Q11(0.5) and R11(0.5), consistent with an almost free rotation of the NO fragment within the complex. The origin of the spectrum is found at 3724.06 cm-1 blue shifted by 0.21 cm-1 from the corresponding NO monomer origin. The rotational structures of the spectrum are found to be in very good agreement with calculated spectra based on bound states derived from a set of high level ab initio potential energy surfaces [Kłos et al. J. Chem. Phys. 112, 2195 (2000)].
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Affiliation(s)
- V Beutner
- Department of Physics and Astronomy, The University of Georgia, Athens, Georgia 30602-2451, USA
| | - S G Zhang
- Department of Physics and Astronomy, The University of Georgia, Athens, Georgia 30602-2451, USA
| | - H Meyer
- Department of Physics and Astronomy, The University of Georgia, Athens, Georgia 30602-2451, USA
| | - J Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA
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Kłos J, Zhang SG, Meyer H. The near-IR spectrum of NO(X̃(2)Π)-Ne detected through excitation into the Ã-state continuum: A joint experimental and theoretical study. J Chem Phys 2016; 144:114307. [PMID: 27004876 DOI: 10.1063/1.4943797] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present new measurements of the near IR spectrum of NO-Ne in the region of the first NO overtone transition. The IR absorption is detected by exciting the vibrationally excited complex to the Ã-state dissociation continuum. The resulting NO(A) fragment is subsequently ionized in the same laser pulse. Spectra of the two lowest bands, A and B, are recorded. The spectra are compared with calculated spectra based on bound states derived from a new set of high level ab initio potential energy surfaces (PESs). For the calculation, the PESs are used with either fixed NO intermolecular distance or averaged for the vibrational states of NO (X̃, v = 0 or 2). Spectra based on the new PESs reproduce the experimental spectra better than theoretical spectra based on the older PESs of M. H. Alexander et al. [J. Chem. Phys. 114, 5588 (2001)]. Especially, spectra based on the two different vibrationally averaged PESs show a marked improvement in comparison to the one based on the fixed internuclear NO-distance. A fitted set of spectroscopic constants allows to reproduce most of the finer details of the measured spectra. Monitoring simultaneously the NO fragment ion and the parent ion channels while scanning the UV wavelength through the NO A-X hot-band region enabled us to confirm the NO-Ne Ã-state dissociation limit of 44233 ± 5 cm(-1). These measurements also confirm the absence of a structured NO-Ne spectrum involving the Ã-state.
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Affiliation(s)
- J Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA
| | - S G Zhang
- Department of Physics and Astronomy, The University of Georgia, Athens, Georgia 30602-2451, USA
| | - H Meyer
- Department of Physics and Astronomy, The University of Georgia, Athens, Georgia 30602-2451, USA
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Perkins T, Herráez-Aguilar D, McCrudden G, Kłos J, Aoiz F, Brouard M. Surface-hopping trajectories for OH(A2Σ+) + Kr: Extension to the 1A″ state. J Chem Phys 2015; 142:144307. [DOI: 10.1063/1.4916972] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- T. Perkins
- The Department of Chemistry, The Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - D. Herráez-Aguilar
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - G. McCrudden
- The Department of Chemistry, The Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - J. Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - F.J. Aoiz
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - M. Brouard
- The Department of Chemistry, The Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
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Bulut N, Castillo J, Jambrina PG, Kłos J, Roncero O, Aoiz FJ, Bañares L. Accurate Time-Dependent Wave Packet Calculations for the O+ + H2 → OH+ + H Ion–Molecule Reaction. J Phys Chem A 2015; 119:11951-62. [DOI: 10.1021/acs.jpca.5b00815] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- N. Bulut
- Department of Physics, Firat University, 23169 Elazig̃, Turkey
| | - J.F. Castillo
- Departamento
de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid (Unidad Asociada I+D+i CSIC), 28040 Madrid, Spain
| | - P. G. Jambrina
- Departamento
de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid (Unidad Asociada I+D+i CSIC), 28040 Madrid, Spain
| | - J. Kłos
- Department of Chemistry
and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, United States
| | - O. Roncero
- Departamento de Física Atómica, Molecular y de Agregados,
Instituto de Física Fundamental, CSIC, C/Serrano, 123, 28006 Madrid, Spain
| | - F. J. Aoiz
- Departamento
de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid (Unidad Asociada I+D+i CSIC), 28040 Madrid, Spain
| | - L. Bañares
- Departamento
de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid (Unidad Asociada I+D+i CSIC), 28040 Madrid, Spain
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Brouard M, Chadwick H, Gordon SDS, Hornung B, Nichols B, Kłos J, Aoiz FJ, Stolte S. Fully quantum state-resolved inelastic scattering of NO(X) + Kr: Differential cross sections and product rotational alignment. J Chem Phys 2014; 141:164306. [DOI: 10.1063/1.4897558] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M. Brouard
- The Department of Chemistry, University of Oxford, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - H. Chadwick
- The Department of Chemistry, University of Oxford, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - S. D. S. Gordon
- The Department of Chemistry, University of Oxford, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - B. Hornung
- The Department of Chemistry, University of Oxford, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - B. Nichols
- The Department of Chemistry, University of Oxford, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - J. Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - F. J. Aoiz
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - S. Stolte
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
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Chadwick H, Brouard M, Chang YP, Eyles CJ, McCrudden G, Perkins T, Seamons SA, Kłos J, Alexander MH, Dagdigian PJ, Herráez-Aguilar D, Aoiz FJ. The collisional depolarization of OH(A 2Σ+) and NO(A 2Σ+) with Kr. J Chem Phys 2014; 140:054306. [DOI: 10.1063/1.4863446] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
Employing the method of constant photon energy sum (CONPHOENERS) scans, we measure the near-IR spectrum of NO-Xe in the region of the first vibrational overtone of the NO monomer. Three bands are detected, which are assigned as the origin band located at 3722.60 cm(-1) and as bands with excitation of one quantum of z-axis rotation (3726.07 cm(-1)) and one quantum of bending vibration (3739.02 cm(-1)), respectively. The partially resolved rotational and electronic fine structures of the bands are analyzed with the help of a full quantum mechanical bound-state calculation using the ab initio potential energy surfaces of Kłos et al. (J. Chem. Phys. 2012, 137, 014312/1-014312/14). We perform a linear least-squares fit to the calculated energy levels to determine a set of spectroscopic constants that describe not only the overall rotation of the complex but also the electrostatic splitting due to the sum potential and the P-type doubling due to the difference potential. Using these results as guidance, we are able to simulate the experimental spectra. The comparison with the results from the theoretical treatment confirms the high quality of the ab initio treatment. The position of the excited bands is predicted with sub-wavenumber accuracy. Also, the rotational constants for all bands are found within less than 5%. Some differences are found for the amount of P-type doubling, which is overestimated by the theoretical treatment. Constants for the electrostatic splitting are in reasonable agreement for the origin band. Larger deviations are found for the vibrationally excited band, which points toward some inaccuracies in the potential energy surfaces.
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Affiliation(s)
- H Meyer
- Department of Physics and Astronomy, The University of Georgia , Athens, Georgia 30602-2451, United States
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Brouard M, Chadwick H, Eyles CJ, Hornung B, Nichols B, Scott JM, Aoiz FJ, Kłos J, Stolte S, Zhang X. The fully quantum state-resolved inelastic scattering of NO(X) + Ne: experiment and theory. Mol Phys 2013. [DOI: 10.1080/00268976.2013.783940] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- M. Brouard
- a Department of Chemistry, The Physical and Theoretical Chemistry Laboratory , University of Oxford , Oxford , United Kingdom
| | - H. Chadwick
- a Department of Chemistry, The Physical and Theoretical Chemistry Laboratory , University of Oxford , Oxford , United Kingdom
| | - C. J. Eyles
- a Department of Chemistry, The Physical and Theoretical Chemistry Laboratory , University of Oxford , Oxford , United Kingdom
| | - B. Hornung
- a Department of Chemistry, The Physical and Theoretical Chemistry Laboratory , University of Oxford , Oxford , United Kingdom
| | - B. Nichols
- a Department of Chemistry, The Physical and Theoretical Chemistry Laboratory , University of Oxford , Oxford , United Kingdom
| | - J. M. Scott
- a Department of Chemistry, The Physical and Theoretical Chemistry Laboratory , University of Oxford , Oxford , United Kingdom
| | - F. J. Aoiz
- b Departamento de Química Física, Facultad de Química , Universidad Complutense , Madrid , Spain
| | - J. Kłos
- c Department of Chemistry and Biochemistry , University of Maryland , College Park , MD , USA
| | - S. Stolte
- d Atomic and Molecular Physics Institute , Jilin University , Changchun , China
- e Laser Center , Vrije Universiteit , Amsterdam , The Netherlands
- f Laboratoire Francis Perrin , Bâtiment 522, DRECEM/SPAM/CEA Saclay, Gif sur Yvette , France
| | - X. Zhang
- d Atomic and Molecular Physics Institute , Jilin University , Changchun , China
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Chadwick H, Brouard M, Chang YP, Eyles CJ, Perkins T, Seamons SA, Kłos J, Alexander MH, Aoiz FJ. A new potential energy surface for OH(A 2Σ+)–Kr: The van der Waals complex and inelastic scattering. J Chem Phys 2012; 137:154305. [DOI: 10.1063/1.4757859] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Poad BLJ, Dryza V, Buchachenko AA, Kłos J, Bieske EJ. Properties of the B+-H2and B+-D2complexes: A theoretical and spectroscopic study. J Chem Phys 2012; 137:124312. [DOI: 10.1063/1.4754131] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kłos J, Aoiz FJ, Menéndez M, Brouard M, Chadwick H, Eyles CJ. Ab Initio studies of the interaction potential for the Xe–NO(X 2Π) van der Waals complex: Bound states and fully quantum and quasi-classical scattering. J Chem Phys 2012; 137:014312. [DOI: 10.1063/1.4731286] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Eyles CJ, Brouard M, Chadwick H, Hornung B, Nichols B, Yang CH, Kłos J, Aoiz FJ, Gijsbertsen A, Wiskerke AE, Stolte S. Fully Λ-doublet resolved state-to-state differential cross-sections for the inelastic scattering of NO(X) with Ar. Phys Chem Chem Phys 2012; 14:5403-19. [PMID: 22434386 DOI: 10.1039/c2cp23258h] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fully Λ-doublet resolved state-to-state differential cross-sections (DCSs) for the collisions of the open-shell NO(X, (2)Π(1/2), ν = 0, j = 0.5) molecule with Ar at a collision energy of 530 cm(-1) are presented. Initial state selection of NO(X, (2)Π(1/2), j = 0.5, f) was performed using a hexapole so that the (low field seeking) parity of ε = -1, corresponding to the f component of the Λ-doublet, could be selected uniquely. Although the Λ-doublet levels lie very close in energy to one another and differ only in their relative parities, they exhibit strikingly different DCSs. Both spin-orbit conserving and spin-orbit changing collisions have been studied, and the previously unobserved structures in the fully quantum state-to-state resolved DCSs are shown to depend sensitively on the change in parity of the wavefunction of the NO molecule on collision. In all cases, the experimental data are shown to be in excellent agreement with rigorous quantum mechanical scattering calculations.
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Affiliation(s)
- C J Eyles
- The Department of Chemistry, University of Oxford, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, UK
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McGurk SJ, McKendrick KG, Costen ML, Bennett DIG, Kłos J, Alexander MH, Dagdigian PJ. Depolarization of rotational angular momentum in CN(A2Π, v = 4) + Ar collisions. J Chem Phys 2012; 136:164306. [PMID: 22559481 DOI: 10.1063/1.4705118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Angular momentum depolarization and population transfer in CN(A(2)Π, v = 4, j, F(1)e) + Ar collisions have been investigated both experimentally and theoretically. Ground-state CN(X(2)Σ(+)) molecules were generated by pulsed 266-nm laser photolysis of ICN in a thermal (nominally 298 K) bath of the Ar collision partner at a range of pressures. The translationally thermalized CN(X) radicals were optically pumped to selected unique CN(A(2)Π, v = 4, j = 2.5, 3.5, 6.5, 11.5, 13.5, and 18.5, F(1)e) levels on the A-X (4,0) band by a pulsed tunable dye laser. The prepared level was monitored in a collinear geometry by cw frequency-modulated (FM) spectroscopy in stimulated emission on the CN(A-X) (4,2) band. The FM lineshapes for co- and counter-rotating circular pump and probe polarizations were analyzed to extract the time dependence of the population and (to a good approximation) orientation (tensor rank K = 1 polarization). The corresponding parallel and perpendicular linear polarizations yielded population and alignment (K = 2). The combined population and polarization measurements at each Ar pressure were fitted to a 3-level kinetic model, the minimum complexity necessary to reproduce the qualitative features of the data. Rate constants were extracted for the total loss of population and of elastic depolarization of ranks K = 1 and 2. Elastic depolarization is concluded to be a relatively minor process in this system. Complementary full quantum scattering (QS) calculations were carried out on the best previous and a new set of ab initio potential energy surfaces for CN(A)-Ar. Collision-energy-dependent elastic tensor and depolarization cross sections for ranks K = 1 and 2 were computed for CN(A(2)Π, v = 4, j = 1.5-10.5, F(1)e) rotational/fine-structure levels. In addition, integral cross sections for rotationally inelastic transitions out of these levels were computed and summed to yield total population transfer cross sections. These quantities were integrated over a thermal collision-energy distribution to yield the corresponding rate constants. A complete master-equation simulation using the QS results for the selected initial level j = 6.5 gave close, but not perfect, agreement with the near-exponential experimental population decays, and successfully reproduced the observed multimodal character of the polarization decays. On average, the QS population removal rate constants were consistently 10%-15% higher than those derived from the 3-level fit to the experimental data. The QS and experimental depolarization rate constants agree within the experimental uncertainties at low j, but the QS predictions decline more rapidly with j than the observations. In addition to providing a sensitive test of the achievable level of agreement between state-of-the art experiment and theory, these results highlight the importance of multiple collisions in contributing to phenomenological depolarization using any method sensitive to both polarized and unpolarized molecules in the observed level.
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Affiliation(s)
- S J McGurk
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
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Eyles CJ, Brouard M, Chadwick H, Aoiz FJ, Kłos J, Gijsbertsen A, Zhang X, Stolte S. The effect of parity conservation on the spin–orbit conserving and spin–orbit changing differential cross sections for the inelastic scattering of NO(X) by Ar. Phys Chem Chem Phys 2012; 14:5420-39. [DOI: 10.1039/c2cp23259f] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Brouard M, Chadwick H, Chang YP, Eyles CJ, Aoiz FJ, Kłos J. Collisional angular momentum depolarization of OH(A) and NO(A) by Ar: A comparison of mechanisms. J Chem Phys 2011; 135:084306. [DOI: 10.1063/1.3625638] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Brouard M, Chadwick H, Eyles CJ, Aoiz FJ, Kłos J. The k-j-j′ vector correlation in inelastic and reactive scattering. J Chem Phys 2011; 135:084305. [DOI: 10.1063/1.3625637] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Poad BLJ, Dryza V, Kłos J, Buchachenko AA, Bieske EJ. Rotationally resolved infrared spectrum of the Na+-D2 complex: An experimental and theoretical study. J Chem Phys 2011; 134:214302. [DOI: 10.1063/1.3596720] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dryza V, Bieske EJ, Buchachenko AA, Kłos J. Potential energy surface and rovibrational calculations for the Mg +–H2 and Mg +–D2 complexes. J Chem Phys 2011; 134:044310. [DOI: 10.1063/1.3530800] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Brahms N, Tscherbul TV, Zhang P, Kłos J, Sadeghpour HR, Dalgarno A, Doyle JM, Walker TG. Formation of van der Waals molecules in buffer-gas-cooled magnetic traps [corrected]. Phys Rev Lett 2010; 105:033001. [PMID: 20867761 DOI: 10.1103/physrevlett.105.033001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 05/29/2010] [Indexed: 05/29/2023]
Abstract
We predict that a large class of helium-containing cold polar molecules form readily in a cryogenic buffer gas, achieving densities as high as 10(12) cm(-3). We explore the spin relaxation of these molecules in buffer-gas-loaded magnetic traps and identify a loss mechanism based on Landau-Zener transitions arising from the anisotropic hyperfine interaction. Our results show that the recently observed strong T(-6) thermal dependence of the spin-change rate of silver (Ag) trapped in dense (3)He is accounted for by the formation and spin change of Ag(3)He van der Waals molecules, thus providing indirect evidence for molecular formation in a buffer-gas trap.
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Affiliation(s)
- N Brahms
- Department of Physics, University of California, Berkeley, California 97420, USA
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Abstract
We report the first measurement of the spectrum of the NO-N(2) complex in the region of the first vibrational NO overtone transition. The origin band of the complex is blueshifted by 0.30 cm(-1) from the corresponding NO monomer frequency. The observed spectrum consists of three bands assigned to the origin band, the excitation of one quantum of z-axis rotation and one associated hot band. The spacing of the bands and the rotational structure indicate a T-shaped vibrationally averaged structure with the NO molecule forming the top of the T. These findings are confirmed by high level ab initio calculations of the potential energy surfaces in planar symmetry. The deepest minimum is found for a T-shaped geometry on the A(")-surface. As a result the sum potential also has the global minimum for this structure. The different potential surfaces show several additional local minima at slightly higher energies indicating that the complex most likely will perform large amplitude motion even in its ground vibrational state. Nevertheless, as suggested by the measured spectra, the complex must, on average, spend a substantial amount of time near the T-shaped configuration.
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Affiliation(s)
- B Wen
- Department of Physics and Astronomy, The University of Georgia, Athens, Georgia 30602-2451, USA
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Lique F, Jorfi M, Honvault P, Halvick P, Lin SY, Guo H, Xie DQ, Dagdigian PJ, Kłos J, Alexander MH. O+OH-->O(2)+H: A key reaction for interstellar chemistry. New theoretical results and comparison with experiment. J Chem Phys 2010; 131:221104. [PMID: 20001016 DOI: 10.1063/1.3274226] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We report extensive, fully quantum, time-independent (TID) calculations of cross sections at low collision energies and rate constants at low temperatures for the O+OH reaction, of key importance in the production of molecular oxygen in cold, dark, interstellar clouds and in the chemistry of the Earth's atmosphere. Our calculations are compared with TID calculations within the J-shifting approximation, with wave-packet calculations, and with quasiclassical trajectory calculations. The fully quantum TID calculations yield rate constants higher than those from the more approximate methods and are qualitatively consistent with a low-temperature extrapolation of earlier experimental values but not with the most recent experiments at the lowest temperatures.
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Affiliation(s)
- F Lique
- LOMC, Universite du Havre, 25 Rue Philippe Lebon, BP 540, 76 058 Le Havre Cedex, France
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Kłos J, Toboła R, Chałasiński G. Inelastic scattering of the NCO(X2Pi) radical with the He atom on an ab initio potential energy surface. J Phys Chem A 2009; 113:14480-7. [PMID: 19681624 DOI: 10.1021/jp903918r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The (2)A' and (2)A'' adiabatic potential energy surfaces for the He-NCO(X(2)Pi) van der Waals system are obtained by the partially spin-restricted coupled cluster method with single, double, and noniterated triple excitations (RCCSD(T)). The ab initio potentials are fit to analytical expressions, and scattering and bound state calculations are performed for a rigid NCO((2)Pi) radical. Rotational constants of the complex are reported. The scattering calculations of integral and differential cross sections are performed using both the fully quantum close-coupling (CC) and coupled-states (CS) methods. The collision energies have the values taken from the experiment of Macdonald and Liu (J. Chem. Phys. 1992, 97, 978). The excellent agreement between theoretical and experimental scattering results attests good quality of the ab initio potential.
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Affiliation(s)
- J Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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Costen ML, Livingstone R, McKendrick KG, Paterson G, Brouard M, Chadwick H, Chang YP, Eyles CJ, Aoiz FJ, Kłos J. Elastic Depolarization of OH(A) by He and Ar: A Comparative Study. J Phys Chem A 2009; 113:15156-70. [DOI: 10.1021/jp905348c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | | | | | | | | | | | - F. J. Aoiz
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - J. Kłos
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
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Aoiz FJ, Verdasco JE, Brouard M, Kłos J, Marinakis S, Stolte S. Inelastic Scattering of He Atoms and NO(X2Π) Molecules: The Role of Parity on the Differential Cross Section. J Phys Chem A 2009; 113:14636-49. [DOI: 10.1021/jp9043732] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. J. Aoiz
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - J. E. Verdasco
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
| | - M. Brouard
- The Department of Chemistry, The Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - J. Kłos
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain, and Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20472
| | - S. Marinakis
- LPMAA, CNRS UMR 7092, Université Pierre et Marie Curie (Paris 6), 3 rue Galilée, 94200 Ivry sur Seine, France
| | - S. Stolte
- Laser Center and Department of Physical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands, and Atomic and Molecular Physics Institute, Jilin University, Changchun 130012, China
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Brouard M, Bryant A, Chang YP, Cireasa R, Eyles CJ, Green AM, Marinakis S, Aoiz FJ, Kłos J. Collisional depolarization of OH(A) with Ar: Experiment and theory. J Chem Phys 2009; 130:044306. [DOI: 10.1063/1.3061551] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Aoiz FJ, Brouard M, Eyles CJ, Kłos J, de Miranda MP. The collisional depolarization of Σ2S+1 radicals by closed shell atoms: Theory and application to OH(A Σ2+)+Ar. J Chem Phys 2009; 130:044305. [DOI: 10.1063/1.3061496] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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33
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Brouard M, Chadwick H, Chang YP, Cireasa R, Eyles CJ, La Via AO, Screen N, Aoiz FJ, Kłos J. Collisional depolarization of NO(A) by He and Ar studied by quantum beat spectroscopy. J Chem Phys 2009. [DOI: 10.1063/1.3212608] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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34
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Toboła R, Chałasiński G, Kłos J, Szczęśniak MM. Ab initio study of the Br([sup 2]P)–HBr van der Waals complex. J Chem Phys 2009; 130:184304. [DOI: 10.1063/1.3123168] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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35
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Poad BLJ, Wearne PJ, Bieske EJ, Buchachenko AA, Bennett DIG, Kłos J, Alexander MH. The Na+–H2 cation complex: Rotationally resolved infrared spectrum, potential energy surface, and rovibrational calculations. J Chem Phys 2008; 129:184306. [DOI: 10.1063/1.3005785] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kłos J, Alexander MH, Brouard M, Eyles CJ, Aoiz FJ. A new potential energy surface for OH(A Σ2+)–Ar: The van der Waals complex and scattering dynamics. J Chem Phys 2008; 129:054301. [DOI: 10.1063/1.2957745] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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37
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Wen B, Kim Y, Meyer H, Kłos J, Alexander MH. IR-REMPI Double Resonance Spectroscopy: The Near-IR Spectrum of NO−Ar Revisited. J Phys Chem A 2008; 112:9483-93. [DOI: 10.1021/jp802765z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Kłos J, Lique F, Alexander M. Quantum scattering of NO(X2Π) with He(1S): Temperature dependence of rotational (de)-excitation rate coefficients. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.02.045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Emmeluth C, Poad BLJ, Thompson CD, Weddle G, Bieske EJ, Buchachenko AA, Grinev TA, Kłos J. The Al+–H2 cation complex: Rotationally resolved infrared spectrum, potential energy surface, and rovibrational calculations. J Chem Phys 2007; 127:164310. [DOI: 10.1063/1.2778422] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kłos J, Aoiz FJ, Verdasco JE, Brouard M, Marinakis S, Stolte S. Fully quantum state-resolved inelastic scattering between He and NO(XΠ2). J Chem Phys 2007; 127:031102. [PMID: 17655424 DOI: 10.1063/1.2756826] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Quantum mechanical close-coupling calculations have been used to obtain fully quantum state-resolved differential cross sections and opacity functions for the rotationally inelastic collisions of NO(X (2)Pi) with He at collision energies of 63 and 147 meV using the most recent ab initio potential energy surfaces of Kłos et al. [J. Chem. Phys. 112, 2195 (2000)]. Double peaks observed in the Lambda-doublet resolved differential cross sections are shown to be related to the presence of analogous peaks in the corresponding opacity functions. These structures can be linked directly to a specific expansion term in the potential, and reflect the fact that NO is not quite homonuclear.
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Affiliation(s)
- J Kłos
- Departamento de Química Física, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
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Abstract
Static properties of a dendrimer with generation g = 5 with positively charged terminal groups in an athermal solvent are studied by lattice Monte Carlo simulations using the cooperative motion algorithm as the tossing scheme. The calculations are performed both for a salt-free system with neutralizing counterions and for a small amount of added monovalent and divalent salt. The full Coulomb potential and the excluded volume interactions between ions and beads are taken explicitly into account with the reduced temperature tau, the number of salt cations (anions) n(s), and salt valence z(s) as the simulation parameters. The bahaviour of the systems is analyzed by the mean effective charge per end-bead <Q>, Coulomb mean energy <E>, mean-square radius of gyration <R(g)(2)>, pair correlation functions g(alphabeta), and charge density rho(ch). The simulations show that for n(s)> or = 0 and decreasing tau: (a) there is encapsulation in the dendrimer and condensation onto the terminal groups of anions accompanied by a monotonic decrease in <Q> and <E> and by subsequent swelling and shrinking of the molecule; (b) encapsulation, condensation and shrinking are the most significant and swelling weaker for |z(s)| = 2; (c) penetration of salt cations into the dendrimer is minor when compared to that of anions; (d) rho(ch) is reduced and becomes negative close to the center of mass of the dendrimer and on its periphery; (e) for the considered n(s) > 0, unlike divalent salt ions the monovalent ones cause slight effects when compared to the salt-free case.
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Affiliation(s)
- M Majtyka
- Max-Planck-Institute for Polymer Research, Postfach 3148, 55021 Mainz, Germany
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Abstract
Using the cooperative motion algorithm, the effect of salt valence z(s) and of the reduced temperature T* on a single polyelectrolyte chain as well as on counterions and salt ions themselves is studied. The calculations show that both parameters strongly influence the polymer, causing it to undergo conformational changes. For a given number of the added salt cations (anions) n(s) and temperature T*, the chain takes more and more compact forms as z(s) increases (z(s) > 0). For fixed z(s), in turn, the polymer size reduces sharply as T* drops down from intermediate to low. For high T* configurational the entropy dominates the chain statistics and the mean-square radius of gyration (s2)1/2(T*,n(s),z(s)) approaches its athermal value. The low-temperature polymer collapse is also accompanied by a drop in the effective mean charge per monomer q*(T*,n(s),z(s)) (condensation of ions onto the chain) and the total inner energy e*(T*,n(s),z(s)). Furthermore, the local structure of the system is analyzed by means of pair-correlation functions g(ab)(r,T*,n(s),z(s)). At lower T* they possess sharp local maxima at small interparticle distances r that disappear as T* grows. The former observation indicates that at lower T* the ions tend to group themselves close to each other. In particular, it is concluded that the condensation is dominated by the multivalent salt ions carrying charges of opposite sign to that of monomers.
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Affiliation(s)
- J Kłos
- Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland.
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Grinev TA, Buchachenko AA, Kłos J, Bieske EJ. Ab initiopotential energy surface, infrared spectra, and dynamics of the ion-molecule complexes between Br− and H2, D2, and HD. J Chem Phys 2006; 125:114313. [PMID: 16999480 DOI: 10.1063/1.2355494] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A three-dimensional potential energy surface (PES) for the Br(-)-H(2) complex is computed using the ab initio CCSD(T) method and an extended basis set. The PES has two equivalent minima at the linear geometries (equilibrium interfragment distance R(e)=3.34 A and interaction energy D(e)=670 cm(-1)) separated by the barrier at the T-shaped configuration (interfragment distance R(e)=4.03 A and barrier height of 610 cm(-1)). Ab initio points are fitted to a flexible analytical form and used in the variational rovibrational energy level calculations. Simulated infrared spectra of the Br(-)-H(2) and Br(-)-D(2) complexes in the monomer stretching excitation region are in good agreement with the measured ones. Nonstatistical intensity ratios of the complexes of para- and ortho-monomers are qualitatively explained by monomer ligand exchange reactions. Predissociation of the complexes containing vibrationally excited monomers is analyzed and shown to proceed through the near-resonant vibration-to-rotation energy transfer. For complexes involving Br(-) and the HD monomer, two energetically low-lying states are predicted, corresponding predominately to the Br(-)-DH and Br(-)-HD isomeric forms. The results demonstrate the close similarity of the bromide containing complexes to their analogs containing the chloride anion.
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Affiliation(s)
- T A Grinev
- Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, Moscow 119992, Russia
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46
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Gijsbertsen A, Linnartz H, Rus G, Wiskerke AE, Stolte S, Chandler DW, Kłos J. Differential cross sections for collisions of hexapole state-selected NO with He. J Chem Phys 2005; 123:224305. [PMID: 16375474 DOI: 10.1063/1.2126969] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The first measurements of differential inelastic collision cross sections of fully state-selected NO (j=12, Omega=12, epsilon= -1) with He are presented. Full state selection is achieved by a 2 m long hexapole, which allows for a systematic study of the effect of parity conservation and breaking on the differential cross section. The collisionally excited NO molecules are detected using a resonant (1+1') REMPI ionization scheme in combination with the velocity-mapped, ion-imaging technique. The current experimental configuration minimizes the contribution of noncolliding NO molecules in other rotational states j, Omega, epsilon--that contaminates images--and allows for study of the collision process at an unprecedented level of detail. A simple method to correct ion images for collision-induced alignment is presented as well and its performance is demonstrated. The present results show a significant difference between differential cross sections for scattering into the upper and lower component of the Lambda-doublet of NO. This result cannot be due to the energy splitting between these components.
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Affiliation(s)
- A Gijsbertsen
- Laser Centre and Department of Physical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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Abstract
Diluted solutions of a single, electrically charged polymer chain, its monovalent counterions and two kinds of multivalent salts are investigated. In particular, the influence of the salt concentrations and valences on the mean effective charge per monomer, total inner energy, radius of gyration and various pair correlation functions of the monomers and free ions are analysed. The calculations show that it is the four-valent and three-valent ions, oppositely charged to the monomers, that mostly occupy the space around the polymer and tremendously increase their number there compared to that in the bulk. Furthermore, reductions in the polymer size and effective charge per monomer appear, especially for increasing amount of the four-valent salt. Thus, there is an evidence for polymer conformational changes associated with the ion condensation onto the chain.
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Affiliation(s)
- J Kłos
- Faculty of Physics, A Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
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Kłos J. Anisotropic dipole polarizability of transition metal atoms: Sc(D2), Ti(F3,P3), V(F4,P4,D6), Ni(F3) and ions: Sc2+(D2), Ti2+(F3,P3). J Chem Phys 2005; 123:24308. [PMID: 16050746 DOI: 10.1063/1.1953447] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Dipole polarizability tensor components and quadrupole moments of transition-metal atoms Sc, Ti, V, Ni, and Cu and ions Sc2+ and Ti2+ are computed using finite field complete active space self-consistent field and multireference configuration interaction ab initio methods. Perpendicular components of the dipole polarizability tensor are calculated from equations involving only parallel components of the polarizability tensor and its average value. Mean polarizability and polarizability anisotropy decrease in the Sc-Ni series. Relativistic effects are accounted for with the Douglas-Kroll Hamiltonian. The consequences of the anisotropic properties of these atoms to their interactions with spherically symmetric rare gases are also discussed.
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Affiliation(s)
- J Kłos
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA.
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Buchachenko AA, Tscherbul TV, Kłos J, Szcześniak MM, Chałasiński G, Webb R, Viehland LA. Interaction potentials of the RG–I anions, neutrals, and cations (RG=He, Ne, Ar). J Chem Phys 2005; 122:194311. [PMID: 16161577 DOI: 10.1063/1.1900085] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Interaction potentials of the iodine atom, atomic cation, and anion with light rare-gas atoms from He to Ar are calculated within the unified ab initio approach using the unrestricted coupled-cluster with singles and doubles and perturbative treatment of triples correlation treatment, relativistic small-core pseudopotential, and an extended basis set. Ab initio points are fit to a flexible analytical function. The calculated potentials are compared with available literature data, assessed in the I(-)-and I+-ion mobility calculations and the Ar-I(-)-anion zero electron kinetic-energy spectra simulations, and analyzed using the correlation rules. The results indicate a high precision of the reported potentials.
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Affiliation(s)
- A A Buchachenko
- Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, Moscow 119992, Russia.
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Kłos J, Pakula T. Lattice Monte Carlo simulations of a charged polymer chain: Effect of valence and concentration of the added salt. J Chem Phys 2005; 122:134908. [PMID: 15847503 DOI: 10.1063/1.1871936] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The configurational properties of a single polyelectrolyte chain accompanied by counterions and added salt are simulated using the cooperative motion algorithm on the face-centered cubic lattice. In particular, a greater emphasis is put on the effect of valence z(s) and concentration of the added positive (negative) salt ions n(s) on the polymer behavior. This is achieved by inspecting two families of systems with widely varying numbers n(s) of monovalent (z(s)=1) or multivalent (z(s)=4) salt ions at two fixed reduced temperatures T*=0.5, 1. The calculations indicate that especially at the lower temperature the addition of some amount of multivalent salt has a tremendous impact on chain conformations compared to the situation with monovalent salt. Even for relatively low concentrations of the former, the mean radius of gyration <s2>(1/2) and the mean end-to-end distance <R2>(1/2) decrease sharply, i.e., the polymer exists in strongly collapsed forms. This reduction of polymer size is also accompanied by a drop in the system inner energy e* and the effective mean charge per monomer q*. The analysis of various pair-correlation functions g(ab)(r) indicates that the latter effect-caused by condensation of ions onto the chain-is dominated by the multivalent ones. Furthermore, it is found that for z(s)=4, the uncondensed salt ions tend to group themselves into small clusters.
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Affiliation(s)
- J Kłos
- Max-Planck-Institute for Polymer Research, Postfach 3148, 55021 Mainz, Germany
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