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Bouallagui A, Zanchet A, Bañares L, García-Vela A. An ab initio study of the photodissociation of CH 2I and CH 2I . Phys Chem Chem Phys 2023. [PMID: 37465906 DOI: 10.1039/d3cp01460f] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
Photodissociation of the CH2I radical and the CH2I+ cation is studied by means of high-level ab initio calculations, including spin-orbit effects. Potential-energy curves (PEC) along the dissociating bond distances involved in some fragmentation pathways of these species are computed for the ground and several excited electronic states. Based on the PECs obtained, the possible photodissociation mechanisms are analyzed and suggested. Significant differences are found between the fragmentation dynamics of the neutral radical and that of the cation. While a relatively simple dissociation dynamics is predicted for CH2I, more complex fragmentation mechanisms involving internal conversion and couplings between different excited electronic states are expected for CH2I+. The species studied here are relevant to atmospheric chemistry, and the present work can help to understand better how their photodissociation may affect chemical processes in the atmosphere.
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Affiliation(s)
- A Bouallagui
- Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA LR01ES09, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092, Tunis, Tunisia
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
| | - A Zanchet
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
| | - L Bañares
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid (Unidad Asociada I+D+i CSIC), 28040 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), 28049 Madrid, Spain
| | - A García-Vela
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
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2
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Chicharro DV, Hrodmarsson HR, Bouallagui A, Zanchet A, Loison JC, García GA, García-Vela A, Bañares L, Marggi Poullain S. Threshold Photoelectron Spectroscopy of the CH 2I, CHI, and CI Radicals. J Phys Chem A 2021; 125:6122-6130. [PMID: 34232644 PMCID: PMC8478278 DOI: 10.1021/acs.jpca.1c03874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
VUV photoionization of the CHnI radicals (with n = 0, 1, and 2) is investigated by means of synchrotron radiation coupled with a double imaging photoion-photoelectron coincidence spectrometer. Photoionization efficiencies and threshold photoelectron spectra (TPES) for photon energies ranging between 9.2 and 12.0 eV are reported. An adiabatic ionization energy (AIE) of 8.334 ± 0.005 eV is obtained for CH2I, which is in good agreement with previous results [8.333 ± 0.015 eV, Sztáray J. Chem. Phys. 2017, 147, 013944], while for CI an AIE of 8.374 ± 0.005 eV is measured for the first time and a value of ∼8.8 eV is estimated for CHI. Ab initio calculations have been carried out for the ground state of the CH2I radical and for the ground state and excited states of the radical cation CH2I+, including potential energy curves along the C-I coordinate. Franck-Condon factors are calculated for transitions from the CH2I(X̃2B1) ground state of the neutral radical to the ground state and excited states of the radical cation. The TPES measured for the CH2I radical shows several structures that correspond to the photoionization into excited states of the radical cation and are fully assigned on the basis of the calculations. The TPES obtained for the CHI is characterized by a broad structure peaking at 9.335 eV, which could be due to the photoionization from both the singlet and the triplet states and into one or more electronic states of the cation. A vibrational progression is clearly observed in the TPES for the CI radical and a frequency for the C-I stretching mode of 760 ± 60 cm-1 characterizing the CI+ electronic ground state has been extracted.
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Affiliation(s)
- David V Chicharro
- Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Helgi Rafn Hrodmarsson
- Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette, France
| | - Aymen Bouallagui
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, C/Serrano, 123, 28006 Madrid, Spain.,Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA LR01ES09, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis, Tunisia
| | - Alexandre Zanchet
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, C/Serrano, 123, 28006 Madrid, Spain
| | - Jean-Christophe Loison
- ISM, Université Bordeaux 1, CNRS, 351 cours de la Libération, 33405 Talence Cedex, France
| | - Gustavo A García
- Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, BP 48, 91192 Gif sur Yvette, France
| | - Alberto García-Vela
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, C/Serrano, 123, 28006 Madrid, Spain
| | - Luis Bañares
- Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.,Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco, 28049 Madrid, Spain
| | - Sonia Marggi Poullain
- Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
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Haakansson CT, Corkish TR, Watson PD, McKinley AJ, Wild DA. The bromide-bromomethyl radical dimer complex: Anion photoelectron spectroscopy and CCSD(T) calculations. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.138060] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Kortyna A, Doney K, Nesbitt DJ. High-resolution infrared spectroscopy of jet cooled CH 2Br radicals: The symmetric CH stretch manifold and absence of nuclear spin cooling. J Chem Phys 2020; 152:134305. [DOI: 10.1063/5.0002165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Andrew Kortyna
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA
| | - Kirstin Doney
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA
| | - D. J. Nesbitt
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
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Kortyna A, Lesko DMB, Nesbitt DJ. High-resolution sub-Doppler infrared spectroscopy of atmospherically relevant Criegee precursor CH 2I radicals: CH 2 stretch vibrations and "charge-sloshing" dynamics. J Chem Phys 2018; 148:174308. [PMID: 29739209 DOI: 10.1063/1.5028287] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The combination of a pulsed supersonic slit-discharge source and single-mode difference frequency direct absorption infrared spectroscopy permit first high resolution infrared study of the iodomethyl (CH2I) radical, with the CH2I radical species generated in a slit jet Ne/He discharge and cooled to 16 K in the supersonic expansion. Dual laser beam detection and collisional collimation in the slit expansion yield sub-Doppler linewidths (60 MHz), an absolute frequency calibration of 13 MHz, and absorbance sensitivities within a factor of two of the shot-noise limit. Fully rovibrationally resolved direct absorption spectra of the CH2 symmetric stretch mode (ν2) are obtained and fitted to a Watson asymmetric top Hamiltonian with electron spin-rotation coupling, providing precision rotational constants and spin-rotation tensor elements for the vibrationally excited state. Analysis of the asymmetric top rotational constants confirms a vibrationally averaged planar geometry in both the ground- and first-excited vibrational levels. Sub-Doppler resolution permits additional nuclear spin hyperfine structures to be observed, with splittings in excellent agreement with microwave measurements on the ground state. Spectroscopic data on CH2I facilitate systematic comparison with previous studies of halogen-substituted methyl radicals, with the periodic trends strongly correlated with the electronegativity of the halogen atom. Interestingly, we do not observe any asymmetric CH2 stretch transitions, despite S/N ≈ 25:1 on strongest lines in the corresponding symmetric CH2 stretch manifold. This dramatic reversal of the more typical 3:1 antisymmetric/symmetric CH2 stretch intensity ratio signals a vibrational transition moment poorly described by simple "bond-dipole" models. Instead, the data suggest that this anomalous intensity ratio arises from "charge sloshing" dynamics in the highly polar carbon-iodine bond, as supported by ab initio electron differential density plots and indeed consistent with observations in other halomethyl radicals and protonated cluster ions.
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Affiliation(s)
- A Kortyna
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA
| | - D M B Lesko
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - D J Nesbitt
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA
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Kapnas KM, Toulson BW, Foreman ES, Block SA, Hill JG, Murray C. UV photodissociation dynamics of CHI 2Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate. Phys Chem Chem Phys 2017; 19:31039-31053. [PMID: 29160321 DOI: 10.1039/c7cp06532a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photolysis of geminal diiodoalkanes in the presence of molecular oxygen has become an established route to the laboratory production of several Criegee intermediates, and such compounds also have marine sources. Here, we explore the role that the trihaloalkane, chlorodiiodomethane (CHI2Cl), may play as a photolytic precursor for the chlorinated Criegee intermediate ClCHOO. CHI2Cl has been synthesized and its UV absorption spectrum measured; relative to that of CH2I2 the spectrum is shifted to longer wavelength and the photolysis lifetime is calculated to be less than two minutes. The photodissociation dynamics have been investigated using DC slice imaging, probing ground state I and spin-orbit excited I* atoms with 2 + 1 REMPI and single-photon VUV ionization. Total translational energy distributions are bimodal for I atoms and unimodal for I*, with around 72% of the available energy partitioned in to the internal degrees of freedom of the CHICl radical product, independent of photolysis wavelength. A bond dissociation energy of D0 = 1.73 ± 0.11 eV is inferred from the wavelength dependence of the translational energy release, which is slightly weaker than typical C-I bonds. Analysis of the photofragment angular distributions indicate dissociation is prompt and occurs primarily via transitions to states of A'' symmetry. Complementary high-level MRCI calculations, including spin-orbit coupling, have been performed to characterize the excited states and confirm that states of A'' symmetry with highly mixed singlet and triplet character are predominantly responsible for the absorption spectrum. Transient absorption spectroscopy has been used to measure the absorption spectrum of ClCHOO produced from the reaction of CHICl with O2 over the range 345-440 nm. The absorption spectrum, tentatively assigned to the syn conformer, is at shorter wavelengths relative to that of CH2OO and shows far weaker vibrational structure.
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Affiliation(s)
- Kara M Kapnas
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA.
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Toulson BW, Alaniz JP, Grant Hill J, Murray C. Near-UV photodissociation dynamics of CH2I2. Phys Chem Chem Phys 2016; 18:11091-103. [DOI: 10.1039/c6cp01063f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The near-UV photodissociation dynamics of CH2I2has been investigated using a combination of velocity-map (slice) ion imaging andab initiocalculations characterizing the excited states.
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Affiliation(s)
| | | | - J. Grant Hill
- Department of Chemistry
- University of Sheffield
- Sheffield S3 7HF
- UK
| | - Craig Murray
- Department of Chemistry
- University of California, Irvine
- Irvine
- USA
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Cheng L. Benchmark calculations on the nuclear quadrupole-coupling parameters for open-shell molecules using non-relativistic and scalar-relativistic coupled-cluster methods. J Chem Phys 2015; 143:064301. [DOI: 10.1063/1.4928054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Lan Cheng
- Department of Chemistry, Institute for Theoretical Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
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Attar AR, Piticco L, Leone SR. Core-to-valence spectroscopic detection of the CH2Br radical and element-specific femtosecond photodissociation dynamics of CH2IBr. J Chem Phys 2015; 141:164308. [PMID: 25362300 DOI: 10.1063/1.4898375] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Element-specific single photon photodissociation dynamics of CH2IBr and core-to-valence absorption spectroscopy of CH2Br radicals are investigated using femtosecond high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy. Photodissociation of CH2IBr along both the C-I or C-Br reaction coordinates is observed in real-time following excitation at 266 nm. At this wavelength, C-I dissociation is the dominant reaction channel and C-Br dissociation is observed as a minor pathway. Both photodissociation pathways are probed simultaneously through individual 4d(I) N(4/5) and 3d(Br) M(4/5) core-to-valence transitions. The 3d(Br) M(4/5) pre-edge absorption spectrum of the CH2Br radical photoproduct corresponding to the C-I dissociation channel is characterized for the first time. Although the radical's singly occupied molecular orbital (SOMO) is mostly localized on the central carbon atom, the 3d(Br) → π*(SOMO) resonances at 68.5 eV and 69.5 eV are detected 2 eV below the parent molecule 3d(Br) → σ*(LUMO) transitions. Core-to-valence XUV absorption spectroscopy provides a unique probe of the local electronic structure of the radical species in reference to the Br reporter atom. The measured times for C-I dissociation leading to I and I* atomic products are 48 ± 12 fs and 44 ± 4 fs, respectively, while the measured C-Br dissociation time leading to atomic Br is 114 ± 17 fs. The investigation performed here demonstrates the capability of femtosecond time-resolved core-level spectroscopy utilizing multiple reporter atoms simultaneously.
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Affiliation(s)
- Andrew R Attar
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Lorena Piticco
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Stephen R Leone
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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Martin-Drumel MA, Pirali O, Balcon D, Bréchignac P, Roy P, Vervloet M. High resolution far-infrared Fourier transform spectroscopy of radicals at the AILES beamline of SOLEIL synchrotron facility. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2011; 82:113106. [PMID: 22128965 DOI: 10.1063/1.3660809] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Experimental far-infrared (FIR) spectroscopy of transient species (unstable molecules, free radicals, and ions) has been limited so far in both emission and absorption (mainly by the low probability of spontaneous emission in that spectral range and the low brightness of continuum sources used for absorption measurements, respectively). Nevertheless, the FIR spectral range recently became of high astrophysical relevance thanks to several new observational platforms (HERSCHEL, ALMA...) dedicated to the study of this region suitable for the detection of the emission from cold objects of the interstellar medium. In order to complete the experimental dataset concerning transient species, three discharge experiments dedicated to the recording of high resolution FIR spectra of radicals have been developed at the Advanced Infrared Line Exploited for Spectroscopy (AILES) which extracts the bright FIR synchrotron continuum of the synchrotron facility SOLEIL. These experiments make use of a high resolution (R = 0.001 cm(-1)) Bruker IFS125 Fourier transform (FT) spectrometer. An emission setup (allowing to record spectra of radicals excited at high rotational and vibrational temperatures) and two absorption setups (exploiting the bright synchrotron source at the highest resolution available on the FT) are alternatively connected to the FT. The advantages and limitations of these techniques are discussed on the basis of the recent results obtained on OH and CH radicals. These results constitute the first FIR spectra of radicals using synchrotron radiation, and the first FIR spectrum of a C-bearing radical using FT-spectroscopy.
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Affiliation(s)
- M A Martin-Drumel
- Institut des Sciences Moléculaires (ISMO), CNRS, Université Paris XI, ba^t. 210, 91405 Orsay Cedex, France.
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El-Khoury PZ, George L, Kalume A, Schapiro I, Olivucci M, Tarnovsky AN, Reid SA. Matrix isolation and computational studies of the CF2I radical. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.07.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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