S-1[-S-0 VIBRONIC SPECTRA AND THE STRUCTURE OF ACETYL FLUORIDE-H(3) AND ACETYL FLUORIDE-D(3) MOLECULES

UV absorption spectra of acetyl fluoride-h(3) and -d(3) (CH3COF and CD 3COF) molecules in the region of S-1<--S-0 electronic transitions are investigated. The origins (0(0)(0) or 14(0)(0+/-)) of these transition s are observed at 39912 and 39904 cm(-1), respectively, and some of th e fundamental frequencies of these molecules in the S-0 and S-1 states are determined. In particular, the systems of torsion and inversion ( out-of-plane C=O vibrations) energy levels are studied. The geometric parameters of an acetyl fluoride-h(3) molecule in the S-1-state are es timated by the theoretical simulation of the rotational contours of th e 0(0)(0) (14(0)(0+/-)) band. These data are used to evaluate the pote ntial barriers to internal rotation in the S-0 and S-1 states, which w ere found to be 360 and 560 cm(-1) for acetyl fluoride-h(3) and 380 an d 770 cm(-1) for acetyl fluoride-d(3), respectively, as well as the po tential barriers to inversion in the S-1 states, which were found to b e 2090 and 2370 cm(-1) for acetyl fluoride-h(3) and acetyl fluoride-d( 3), respectively.