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A full-dimensional ab initio potential energy surface and rovibrational spectra for the Ar–SO2 complex. Theor Chem Acc 2022. [DOI: 10.1007/s00214-022-02914-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Collisional excitation of HNC by He found to be stronger than for structural isomer HCN in experiments at the low temperatures of interstellar space. Nat Chem 2022; 14:811-815. [PMID: 35513509 DOI: 10.1038/s41557-022-00936-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 03/25/2022] [Indexed: 11/08/2022]
Abstract
HCN and its unstable isomer HNC are widely observed throughout the interstellar medium, with the HNC/HCN abundance ratio correlating strongly with temperature. In very cold environments HNC can even appear more abundant than HCN. Here we use a chirped pulse Fourier transform spectrometer to measure the pressure broadening of HCN and HNC, simultaneously formed in situ by laser photolysis and cooled to low temperatures in uniform supersonic flows of helium. Despite the apparent similarity of these systems, we find the HNC-He cross section to be more than twice as big as the HCN-He cross section at 10 K, confirming earlier quantum calculations. Our experimental results are supported by high-level scattering calculations and are also expected to apply with para-H2, demonstrating that HCN and HNC have different collisional excitation properties that strongly influence the derived interstellar abundances.
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Chefai A, Ben Khalifa M, Khadri F, Hammami K. Rotational (de)-excitation of C 5 by collision with He at low temperature. Phys Chem Chem Phys 2021; 23:23741-23747. [PMID: 34643208 DOI: 10.1039/d1cp02652f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An appropriate estimation of the abundance of the observed C5 radical in the interstellar medium requires accurate radiative and collisional rate coefficients. We present the first two-dimensional potential energy surface (2D-PES) for the ground electronic state of the C5(X1Σ+)-He(X1S) van der Waals system, obtained using an explicitly correlated coupled-cluster method with single, double, and perturbative triple excitations (RCCSD(T)-F12). This PES is subsequently used in quantum close-coupling (CC) scattering calculations. Collisional excitation cross-sections of the rotational levels of C5 by He were calculated for energies up to 1500 cm-1 using the standard (CC) method. The thermal dependence of the corresponding rate coefficients is given for the low and moderate temperature T ≤ 300 K regime of interstellar molecular clouds. This is the first study on the collisional rate coefficients for this system and may have important implications for the astrophysical detection of C5(X1Σ+) and modeling of carbon-rich media.
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Affiliation(s)
- A Chefai
- Laboratory of Atomic Molecular Spectroscopy and Applications, Department of Physics, Faculty of Sciences, University Tunis El Manar, Campus Universities 1060, Tunis, Tunisia.
| | - M Ben Khalifa
- Laboratory of Atomic Molecular Spectroscopy and Applications, Department of Physics, Faculty of Sciences, University Tunis El Manar, Campus Universities 1060, Tunis, Tunisia.
| | - F Khadri
- Laboratory of Atomic Molecular Spectroscopy and Applications, Department of Physics, Faculty of Sciences, University Tunis El Manar, Campus Universities 1060, Tunis, Tunisia.
| | - K Hammami
- Laboratory of Atomic Molecular Spectroscopy and Applications, Department of Physics, Faculty of Sciences, University Tunis El Manar, Campus Universities 1060, Tunis, Tunisia.
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Finenko AA, Chistikov DN, Kalugina YN, Conway EK, Gordon IE. Fitting potential energy and induced dipole surfaces of the van der Waals complex CH 4-N 2 using non-product quadrature grids. Phys Chem Chem Phys 2021; 23:18475-18494. [PMID: 34612387 DOI: 10.1039/d1cp02161c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present an extensive study of the five-dimensional potential energy and induced dipole surfaces of the CH4-N2 complex assuming rigid-rotor approximation. Within the supermolecular approach, ab initio calculations of the interaction energies and dipoles were carried out at the CCSD(T)-F12 and CCSD(T) levels of theory using the correlation-consistent aug-cc-pVTZ basis set, respectively. Both potential energy and induced dipole surfaces inherit the symmetry of the molecular system and transform under the A1+ and A2+ irreducible representations of the molecular symmetry group G48, respectively. One can take advantage of the symmetry when fitting the surfaces; first, when constructing angular basis functions and second, when selecting the grid points. The approach to the construction of scalar and vectorial basis functions exploiting the eigenfunction method [Q. Chen, J. Ping and F. Wang, Group Representation Theory for Physicists, World Scientific, 2nd edn, 2002] is developed. We explore the use of Sobolev-type quadrature grids as building blocks of robust quadrature rules adapted to the symmetry of the molecular system. Temperature variations of the cross second virial coefficient and first classical spectral moments of the rototranslational collision-induced band were derived. A reasonable agreement between calculated values and experimental data was found attesting to the high quality of constructed surfaces.
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Affiliation(s)
- Artem A Finenko
- Center for Astrophysics
- Harvard & Smithsonian, Atomic and Molecular Physics Division, 60 Garden Street, Cambridge, MA 02138, USA.
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Ben Khalifa M, Wiesenfeld L, Hammami K. Interaction of the simple carbene c-C3H2with H2: potential energy surface and low-energy scattering. Phys Chem Chem Phys 2019; 21:9996-10002. [DOI: 10.1039/c9cp01601e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclopropenylidene, c-C3H2, is a simple hydrocarbon, ubiquitous in astrophysical gases, and possessing a permanent electric dipole moment.
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Affiliation(s)
- M. Ben Khalifa
- Laboratoire Aimé-Cotton, CNRS, Université Paris-Saclay
- France
- LSAMA, Université de Tunis El Manar
- Tunis
- Tunisia
| | - L. Wiesenfeld
- Laboratoire Aimé-Cotton, CNRS, Université Paris-Saclay
- France
| | - K. Hammami
- LSAMA, Université de Tunis El Manar
- Tunis
- Tunisia
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Shirkov L, Sladek V. Benchmark CCSD-SAPT study of rare gas dimers with comparison to MP-SAPT and DFT-SAPT. J Chem Phys 2017; 147:174103. [DOI: 10.1063/1.4997569] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Leonid Shirkov
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland
| | - Vladimir Sladek
- Institute of Chemistry–Centre for Glycomics, Slovak Academy of Sciences, 845 38 Bratislava, Slovakia
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Raston PL, Jäger W. Rotational Spectroscopic Study of Quantum Solvation in Isotopologic ( pH 2) N–CO Clusters. J Phys Chem A 2017; 121:3671-3678. [DOI: 10.1021/acs.jpca.7b02192] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul L. Raston
- Department
of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807, United States
| | - Wolfgang Jäger
- Department
of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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Nasri S, Ajili Y, Jaidane NE, Kalugina YN, Halvick P, Stoecklin T, Hochlaf M. Potential energy surface of the CO2-N2 van der Waals complex. J Chem Phys 2015; 142:174301. [PMID: 25956094 DOI: 10.1063/1.4919396] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Four-dimensional potential energy surface (4D-PES) of the atmospherically relevant CO2-N2 van der Waals complex is generated using the explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in conjunction with the augmented correlation consistent triple zeta (aug-cc-pVTZ) basis set. This 4D-PES is mapped along the intermonomer coordinates. An analytic fit of this 4D-PES is performed. Our extensive computations confirm that the most stable form corresponds to a T-shape structure where the nitrogen molecule points towards the carbon atom of CO2. In addition, we located a second isomer and two transition states in the ground state PES of CO2-N2. All of them lay below the CO2 + N2 dissociation limit. This 4D-PES is flat and strongly anisotropic along the intermonomer coordinates. This results in the possibility of the occurrence of large amplitude motions within the complex, such as the inversion of N2, as suggested in the recent spectroscopic experiments. Finally, we show that the experimentally established deviations from the C2v structure at equilibrium for the most stable isomer are due to the zero-point out-of-plane vibration correction.
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Affiliation(s)
- Sameh Nasri
- Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA, Université de Tunis El Manar, Tunis, Tunisia
| | - Yosra Ajili
- Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA, Université de Tunis El Manar, Tunis, Tunisia
| | - Nejm-Eddine Jaidane
- Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA, Université de Tunis El Manar, Tunis, Tunisia
| | - Yulia N Kalugina
- Department of Optics and Spectroscopy, Tomsk State University, 36 Lenin Ave., Tomsk 634050, Russia
| | - Philippe Halvick
- Institut des Sciences Moléculaires, Université de Bordeaux, CNRS UMR 5255, 33405 Talence Cedex, France
| | - Thierry Stoecklin
- Institut des Sciences Moléculaires, Université de Bordeaux, CNRS UMR 5255, 33405 Talence Cedex, France
| | - Majdi Hochlaf
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France
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Berg M, Accardi A, Paulus B, Schmidt B. Rotationally adiabatic pair interactions of para- and ortho-hydrogen with the halogen molecules F2, Cl2, and Br2. J Chem Phys 2014; 141:074303. [PMID: 25149782 DOI: 10.1063/1.4892599] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The present work is concerned with the weak interactions between hydrogen and halogen molecules, i.e., the interactions of pairs H2-X2 with X = F, Cl, Br, which are dominated by dispersion and quadrupole-quadrupole forces. The global minimum of the four-dimensional (4D) coupled cluster with singles and doubles and perturbative triples (CCSD(T)) pair potentials is always a T shaped structure where H2 acts as the hat of the T, with well depths (De) of 1.3, 2.4, and 3.1 kJ/mol for F2, Cl2, and Br2, respectively. MP2/AVQZ results, in reasonable agreement with CCSD(T) results extrapolated to the basis set limit, are used for detailed scans of the potentials. Due to the large difference in the rotational constants of the monomers, in the adiabatic approximation, one can solve the rotational Schrödinger equation for H2 in the potential of the X2 molecule. This yields effective two-dimensional rotationally adiabatic potential energy surfaces where pH2 and oH2 are point-like particles. These potentials for the H2-X2 complexes have global and local minima for effective linear and T-shaped complexes, respectively, which are separated by 0.4-1.0 kJ/mol, where oH2 binds stronger than pH2 to X2, due to higher alignment to minima structures of the 4D-pair potential. Further, we provide fits of an analytical function to the rotationally adiabatic potentials.
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Affiliation(s)
- Matthias Berg
- Institut für Chemie, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany
| | - Antonio Accardi
- Institut für Chemie, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany
| | - Beate Paulus
- Institut für Chemie, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany
| | - Burkhard Schmidt
- Institut für Mathematik, Freie Universität Berlin, Arnimallee 6, D-14195 Berlin, Germany
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Kalugina YN, Buryak IA, Ajili Y, Vigasin AA, Jaidane NE, Hochlaf M. Explicit correlation treatment of the potential energy surface of CO2 dimer. J Chem Phys 2014; 140:234310. [DOI: 10.1063/1.4882900] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Vera MH, Kalugina Y, Denis-Alpizar O, Stoecklin T, Lique F. Rotational excitation of HCN by para- and ortho-H2. J Chem Phys 2014; 140:224302. [DOI: 10.1063/1.4880499] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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