Difluorocarbene studied with threshold photoelectron spectroscopy (TPES): measurement of the first adiabatic ionization energy (AIE) of CF2.

[摘要]：The first photoelectron band of difluorocarbene CF2, has been studied by threshold photoelectron (TPE) spectroscopy. CF2 was prepd. by microwave discharge of a flowing mixt. of hexafluoropropene, C3F6, and argon. A vibrationally resolved band was obsd. in which at least twenty-two components were obsd. In the first PE band of CF2, the adiabatic ionization energy differs significantly from the vertical ionization energy because, for the ionization CF2+(X3A1)+e- ? CF2(X1A1), there is an increase in the FCF bond angle (by u20? and a decrease in the C-F bond length (by u0.7 ?. The adiabatic component was not obsd. in the exptl. TPE spectrum. However, on comparing this spectrum with an ab initio/Franck-Condon simulation of this band, using results from high-level ab initio calcns., the structure assocd. with the vibrational components could be assigned. This led to alignment of the exptl. TPE spectrum and the computed Franck-Condon envelope, and a detn. of the first adiabatic ionization energy of CF2 as (11.362 ?0.005) eV. From the assignment of the vibrational structure, values were obtained for the harmonic and fundamental frequencies of the sym. stretching mode (n1') and sym. bending mode (n2') in CF2+(X2A1).

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