Reference : The vacuum UV photoabsorption spectrum of methyl bromide (CH3Br) and its perdeuterated i...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
The vacuum UV photoabsorption spectrum of methyl bromide (CH3Br) and its perdeuterated isotopomer CD3Br: a Rydberg series analysis
[fr] Le spectre de photoabsorption UV sous vide du Bromure de Methyl (CH3Br) et de son isotopomère CD3Br: une analyse des séries de Rydberg.
Locht, Robert mailto [Université de Liège - ULg > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences) >]
Leyh, Bernard mailto [Université de Liège - ULg > Département de chimie (sciences) > Laboratoire de dynamique moléculaire >]
Jochims, H.-W. [Freie Universität Berlin > Institut für Physikalische Chemie > > >]
Baumgärtel, H. [Freie Universität Berlin > Institut fûr Physikalische Chemie > > >]
Chemical Physics
Elsevier Science Bv
[en] photoabsorption ; Rydberg series ; CH3Br ; CD3Br ; exchange interaction ; spin-orbit coupling
[en] The vacuum UV photoabsorption spectrum of CH3Br has been recorded between 6 and 25 eV. A large number of vibronic bands are observed. They were partly ascribed to vibrationless Rydberg transitions. In the high photon energy range of 12-25 eV, very weak diffuse bands are mostly assigned to transitions from the 3a(1), 1e and (2a(1) + 1a(1)) to 3s orbitals. In the 6-12 eV photon energy range, numerous weak to strong bands are observed. The sharpness is very variable over the entire spectral region. In a first step, the interpretation of the spectrum and the assignment of the Rydberg transitions is based on the simple Rydberg formula. The observed features are classified in two groups of four series, each converging to one of the two spin-orbit components of the (X) over tilde E-2 state of CH3Br+. Rydberg series of nsa(1), npa(1), npe, nd and possibly nf characters are observed. The same measurements have been made for the first time on CD3Br in the 6-12 eV photon energy range. The observed features are classified into the same Rydberg series characterized by nearly the same delta values. Ionization energies for CD3Br (X) over tilde (2) E-3/2 at 10.565 eV and (X) over tilde (2) E-1/2 at 10.902 eV are deduced. In a second step, we fitted the experimental data to an energy expression taking into account both the exchange interaction and the spin-orbit coupling. Already states with n = 6 are found to correspond to Hund's case (c). Constant values of the quantum defects are deduced. (C) 2005 Elsevier B.V. All rights reserved.
Laboratoire de Dynamique Moléculaire - BESSY Berlin, Germany
European Community: TMR Program: EU-HPRI-1999CT-00028, ARC-Belgium, BFT-Germany
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