Temperature Dependence of Air-Broadening and Shift Coefficients of O3 Lines in the nu1 Band

Reaction coordinate analysis of the S1-S0 internal conversion of azulene

The reaction coordinate of the S(1)-S(0) internal conversion of azulene has been analyzed using ab initio complete active space self-consistent field method. The stable geometry in S(0) (S(0) geometry) takes a bond-equalized structure where all the peripheral skeletal bond distances are similar to an aromatic CC bond distance. The transannular bond is similar to a normal C-C single bond. The first event upon electronic excitation into S(1) at S(0) geometry is characterized by the following two simultaneous changes in the skeletal bonds; the transannular bond in S(1) increases its double bond character and the aromaticity of the peripheral bonds disappears. In consequence, the most stable azulene in S(1) (S(1) geometry) has a biradical character. To reach the conical intersection between S(1) and S(0) (S(1)S(0)-CIX) where radiationless relaxation takes place, the seven-membered ring greatly deviates from a planar structure. After a transition into S(0) at S(1)S(0)-CIX, the bond-equalized structure is recovered immediately and then the nonplanarity decreases so that azulene again takes the stable planar S(0) geometry. In order to deepen the understanding of the S(1)-S(0) internal conversion, the dipole moments along the reaction coordinate have been analyzed.

Relaxation and Lineshape of the 500.4-GHz Line of Ozone Perturbed by N(2) and O(2)

N(2)- and O(2)-broadened linewidths of the J = 34(2,32) <-- 34(1,33) transition of ozone located at 500.4 GHz have been measured at three temperatures in the 247-295 K range by using a video-type spectrometer. Besides the Voigt profile commonly used as theoretical model for millimeter-wave investigations, different other theoretical lineshapes, the speed-dependent Voigt profile, the Galatry profile, and the speed-dependent Galatry profile, have been considered to analyze the experimental spectra, to retrieve the pressure-broadening parameters, and to give an account of the pointed out line-narrowing effect. The results for O(3) perturbed by N(2) and O(2) are finally compared to calculations based on the complex semiclassical theory of Robert and Bonamy, and with previous reported values involving the same kind of transitions. Finally, it is shown that observed line narrowings result nearly exclusively from the dependence of relaxation on molecular speeds. Copyright 2000 Academic Press.