EPR and IR spectra of the FS O3 radical revisited: Strong vibronic interactions in the A22 electronic ground state

Abstract

The previous controversy about the ground-state symmetry and contradictory vibrational analyses of FS O3 has been solved by a reinvestigation of its EPR and IR matrix spectra. The anisotropic EPR spectrum of FS O3 isolated in an argon matrix at 5 K is in agreement with an axial symmetry and an A22 electronic ground state. While the obtained hyperfine-coupling constants agree quite well to previous measurements in different environments, the g values may be affected by the large motion of the low-lying (162 cm-1) rocking mode of FS O3. For the first time measurements of the IR matrix spectra were extended to the far infrared region and to all O 1618 isotopomers of FS O3. A new fundamental at 161.6 cm-1 in Ar matrix and, for the nine strongest bands of FS O3, the isotopic O 1618 pattern have been observed and analyzed. The four line pattern of the a1 -type fundamental modes at 1052.7, 832.5, and 531.0 cm-1 confirmed the C3v symmetry of FS O3 in the electronic ground state. The e -type fundamental modes at 931.6, 426.2, and 161.6 cm-1 are unusually low in energy and in intensity due to vibronic interaction to the low-lying electronic excited E2 states. On the other hand, several combinations and overtones of e -type fundamentals are strongly enhanced due to vibronic interactions. © 2008 American Institute of Physics.