کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9575218 | 1389393 | 2005 | 16 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
The vacuum UV photoabsorption spectrum of methyl bromide (CH3Br) and its perdeuterated isotopomer CD3Br: a vibrational analysis
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
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 2E state (in the C3v symmetry group) splits into 2Aâ² and 2Aâ³ states in the CS symmetry group. Even though the energy difference of about 1 meV is extremely small, the 2Aâ² state is energetically the lowest component whereas the 2Aâ³ 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., hcÏ4 = 146 ± 6 meV (1178 ± 48 cmâ1), hcÏ5 = 107 ± 6 meV (863 ± 48 cmâ1) and hcÏ6 = 71 ± 4 meV (572 ± 32 cmâ1), respectively, as resulting from an average over all analyzed Rydberg states. In CD3Br the corresponding energies are hcÏ4 = 104 ± 3 meV (839 ± 24 cmâ1), hcÏ5=82 ± 4 meV (661 ± 32 cmâ1) and hcÏ6 = 62 ± 4 meV (500 ± 32 cmâ1). 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 Ïi = [Ï/Ïisot]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 Ï6, Ï5 and Ï4. On the basis of the present study an alternative assignment of the CH3Br+(XË2E) photoelectron band structure is proposed.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Physics - Volume 317, Issue 1, 10 October 2005, Pages 87-102
Journal: Chemical Physics - Volume 317, Issue 1, 10 October 2005, Pages 87-102
نویسندگان
R. Locht, B. Leyh, D. Dehareng, H.W. Jochims, H. Baumgärtel,