A high magnetic field study of the triplet state of hexachlorobenzene

An analysis of the high-field Zeeman effects of (0,0), 0 + 195 cm(-1), 0+254 cm(-1), 0+359 cm(-1) and 0 + 1139 cm(-1) vibronic transitions in the lowest triplet state of hexachlorobenzene are presented. The studies refer to crystals at 4.2 degrees K in fields of ca. 80 kG. The results show that 195 cm(-1) is an upper state e(g) mode, 254 cm(-1) is probably eg but perhaps a(2g) , and 359 cm(-1) and 1199 cm(-1) are a(g) vibrations. The molecular symmetry is shown to be different from D-3d as far as spin-orbit selection rules are concerned (as expected from the known crystal structure) but as expected no evidence of the crystal field mixing (of D-3d states) appears in the non-totally symmetric vibronic bands. The distribution of electric-dipole strength over the various spin sub-states is deduced for each type of vibronic level.