photoabsorption; vacuum UV; Rydberg series; CH3Br; Jahn-Teller effect; CD3Br; vibrational analysis; Ab initio calculations; photoelectron spectrum
Abstract :
[en] The fine structure of the vacuum UV photoabsorption spectrum of CH3Br and CD3Br has been analyzed in the 6.9-10.2 eV photon energy range. A large number of lines have been observed, classified and assigned to the vibrational excitation accompanying a series of Rydberg transitions. The effects of the Jahn-Teller distortion and of the spin-orbit splitting of the ground electronic state of the ion have been considered. The former effect has been evaluated by ab initio calculations, showing that the E-2 state (in the C-3v symmetry group) splits into (2)A' and (2)A" states in the C-s symmetry group. Even though the energy difference of about 1 meV is extremely small, the (2)A' state is energetically the lowest component whereas the (2)A" is found to be a transition state. The Jahn-Teller stabilization energy and the wavenumbers associated with all vibrational modes have been calculated. Experimentally, the entire fine structure could be described in terms of three vibrational modes, i.e., hc omega(4) = 146 +/- 6 meV (1178 +/- 48 cm(-1)), hc omega(5) = 107 +/- 6 meV (863 +/- 48 cm(-1)) and hc omega(6) = 71 +/- 4 meV (572 +/- 32 cm(-1)), respectively, as resulting from an average over all analyzed Rydberg states. In CD3Br the corresponding energies are hc omega(4) = 104 +/- 3 meV (839 +/- 24 cm(-1)), hc omega(5)=82 +/- 4 meV (661 +/- 32 cm(-1)) and hc omega(6) = 62 +/- 4 meV (500 +/- 32 cm(-1)). These values are in fairly good agreement with those predicted by the present ab initio calculations for the ionic ground state. The experimental isotopic ratio rho(i) = [omega/omega(isot)](i) is 1.15 +/- 0.14, 1.31 +/- 0.14 and 1.39 +/- 1.0 and is predicted to be 1.04, 1.34 and 1.36, respectively, for omega(6), omega(5) and omega(4). On the basis of the present study an alternative assignment of the CH3Br+((X) over tilde E-2) photoelectron band structure is proposed. (C) 2005 Elsevier B.V. All rights reserved.
Research center :
Laboratoire de Dynamique Moléculaire, BESSY Berlin
Disciplines :
Chemistry
Author, co-author :
Locht, Robert ; Université de Liège - ULiège > Département de chimie > Laboratoire de dynamique Moléculaire (Sciences)
Leyh, Bernard ; Université de Liège - ULiège > Département de chimie (sciences) > Laboratoire de dynamique moléculaire
Dehareng, Dominique ; Université de Liège - ULiège > Centre d'ingénierie des protéines
Jochims, Hans-Werner; Freie Universität Berlin > Institut für Physikalische Chemie
Baumgärtel, H.; Freie Universität Berlin > Institut fûr Physikalische Chemie
Language :
English
Title :
The vacuum UV photoabsorption spectrum of methyl bromide (CH3Br) and its perdeuterated isotopomer CD3Br: a vibrational analysis
Alternative titles :
[fr] Le spectre de photoabsorption UV sous vide du Bromure de Méthyl (CH3Br) et de son isotopomère CD3Br: une analyse vibrationnelle.
R. Locht, B. Leyh, A. Hoxha, D. Dehareng, H.W. Jochims, and H. Baumgärtel Chem. Phys. 257 2000 283
R. Locht, B. Leyh, A. Hoxha, H.W. Jochims, and H. Baumgärtel Chem. Phys. 272 2001 259
R. Locht, B. Leyh, A. Hoxha, D. Dehareng, H.W. Jochims, and H. Baumgärtel Chem. Phys. 272 2001 277
R. Locht, B. Leyh, H.W. Jochims, H. Baumgärtel, Chem. Phys., this issue, doi: 10.1016/j.chemphys.2005.06.002.
G.C. Causley, and B.R. Russell J. Chem. Phys. 62 1975 848
S. Felps, P. Hochmann, P. Brint, and S.P. McGlynn J. Mol. Spectrosc. 59 1976 355
A. Hoxha, R. Locht, B. Leyh, K. Hottmann, H.W. Jochims, and H. Baumgärtel Chem. Phys. 260 2000 237
C.L. Lugez, D. Forney, M.E. Jacox, and K.K. Ikura J. Chem. Phys. 106 1997 489
L. Karlsson, R. Jadrny, L. Mattsson, F.T. Chau, and K. Siegbahn Phys. Scripta 16 1977 225
M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery, T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Peterson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvdor, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Karkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.V. Ortiz, J.B. Foresman, Q. Cui, A.G. Baboul, S. Clifford, J. Ciolowski, B.B. Stefanow, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, and J.A. Pople Gaussian-03 (Revision B04) 2003 Gaussian, Inc. Pittsburgh, PA
C. Møller, and M.S. Plesset Phys. Rev. 46 1934 618
M. Head-Gordon, J.A. Pople, and M.J. Frisch Chem. Phys. Lett. 153 1988 503
J.A. Pople, M. Head-Gordon, and K. Raghavachari J. Chem. Phys. 87 1987 5968
G.E. Scuseria, and H.F. Schaefer III J. Chem. Phys. 90 1989 3700
R.G. Parr, and W. Yang Density Functional Theory of Atoms and Molecules 1989 Oxford University Press New York
A.D. Becke J. Chem. Phys. 98 1993 5648
R. Krishnan, J.S. Blinkley, R. Seeger, and J.A. Pople J. Chem. Phys. 72 1980 650
M.J. Frisch, J.A. Pople, and J.S. Binkley J. Chem. Phys. 80 1984 3265
D.E. Woon, and T.H. Dunning Jr. J. Chem. Phys. 98 1993 1358
A.P. Scott, and L. Radom J. Phys. Chem. 100 1996 16502
G. Herzberg Molecular Spectra and Molecular Structure. III. Electronic Spectra and Electronic Structure of Polyatomic Molecules 1967 D. Van Nostrand Princeton, NJ
G. Herzberg Molecular Spectra and Molecular Structure. II. Infrared and Raman Spectra of Polymotic Molecules 1945 D. Van Nostrand New York
R. Locht, E. Gridelet, to be published.
E.R. Cohen, and B.N. Taylor J. Phys. Chem. Ref. Data 37 1973 663
