کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5427454 | 1508631 | 2016 | 12 صفحه PDF | دانلود رایگان |
- S1âS0 vibronic gas-phase absorption spectrum of cyclopropanecarboxaldehyde (CPCA).
- S1âS0 fluorescence excitation spectrum of CPCA.
- Ab initio calculation for CPCA in S0 and S1 electronic states.
- Structural changes of the CPCA at S1âS0 electronic excitation.
The S1âS0 vibronic spectra of gas-phase absorption at room temperature and fluorescence excitation of jet-cooled cyclopropanecarboxaldehyde (CPCA, c-C3H5CHO)were obtained and analyzed. In addition, the quantum chemical calculation (CASPT2/cc-pVTZ)was carried out for CPCA in the ground (S0) and lowest excited singlet (S1) electronic states. As a result, it was proved that the S1âS0 electronic excitation of the CPCA conformers (syn and anti) causes (after geometrical relaxation) significant structural changes, namely, the carbonyl fragments become non-planar and the cyclopropyl groups rotate around the central C-C bond. As a consequence, the potential energy surface of CPCA in the S1 state has six minima, 1ab, 2ab, and 3ab, corresponding to three pairs of mirror symmetry conformers: a and b. It was shown that vibronic bands of experimental spectra can be assigned to the 2(S1)âsyn(S0) electronic transition with the origin at 30,481 cmâ1. A number of fundamental vibrational frequencies for the 2 conformer of CPCA were assigned. In addition, several inversional energy levels for the 2 conformer were found and the 2aâ2b potential function of inversion was determined. The experimental barrier to inversion and the equilibrium angle between the CH bond and the CCO plane were calculated as 570 cmâ1 and 28°, respectively.
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Journal: Journal of Quantitative Spectroscopy and Radiative Transfer - Volume 184, November 2016, Pages 341-352