EPR and IR spectra of the FSO3 radical revisited: Strong vibronic interactions in the 2A2 electronic ground state

The previous controversy about the ground-state symmetry and contradictory vibrational analyses of FSO3 has been solved by a reinvestigation of its EPR and IR matrix spectra. The anisotropic EPR spectrum of FSO3 isolated in an argon matrix at 5 K is in agreement with an axial symmetry and an 2A2 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 FSO3. For the first time measurements of the IR matrix spectra were extended to the far infrared region and to all 16/18 O isotopomers of FSO3. A new fundamental at 161.6 cm(-1) in Ar matrix and, for the nine strongest bands of FSO3, the isotopic 16/18 O 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 FSO3 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 2E states. On the other hand, several combinations and overtones of e-type fundamentals are strongly enhanced due to vibronic interactions.