Mixing of the vibrational angular momentum components of multiply degenerate vibronic states of benzene by vibrational l-type resonance
The rotationally resolved spectra of the 6011002 and 6011602 vibronic transitions of benzene at low rotational temperat reported and analyzed in detail. Deperturbed spectroscopic constants for the 61102 and 61162 states are reported which reproduce the observed line positions to within experimental accuracy. The splitting of 17.9 cm\u22121 between the two subbands of the 6011002 transition and of 6.2 cm\u22121 for the 6011602 transition is found to be due to vibrational l-type resonances with matrix element 8.91 and 2.65 cm\u22121, respectively. These large resonances cause strong distortions of the rotational structure and mix the vibrational angular momentum substates \u03bd6minus-or-plus sign + 2\u03bd100 and \u03bd6\xb1 + 2\u03bd10\xb12 nearly completely and the substates \u03bd6minus-or-plus sign + 2\u03bd160 and \u03bd6\xb1 + 2\u03bd16minus-or-plus sign2 substantially. The importance of the mixing for the intramolecular vibrational redistribution (IVR) and the decay behaviour of S1 benzene is discussed.