The vibronic spectrum of the 2,2-difluoroethanal vapor was recorded using a multipass optical cell with an optical length of at least 140 m. The spectrum in the region of 300—364 nm was assigned to the S
1S
0 electronic transition (from the ground S
0 to the first excited singlet S
1 electronic state); the vibrational structure of the spectrum was analyzed. The spectrum bands were assigned to two systems of vibronic transitions, namely, transitions between the levels of the
cis-conformer (S
0) and of the S
1 conformers, with the origins (0
0
0 transitions between the zero vibrational levels of conformers) at 29192 and 29087 cm
–1, respectively. Analysis of the spectrum showed that the S
1S
0 electronic excitation of the
cis-conformer was followed by rotation of the CHF
2 top and pyramidal distortion of the carbonyl fragment. A number of fundamental frequencies were found for S
1 conformers, in particular, torsion and inversion energy levels. The experimental data are in satisfactory agreement with the results of quantum-chemical calculations for the 2,2-difluoroethanal molecule in the S
0 and S
1 states.
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