Coupling of the ν₇ CH stretch with ring modes in S₁ benzene

The coupling of CH stretch to ring motion has been probed in S₁ benzene by analysing the 7¹ dispersed fluorescence spectrum. The spectrum reveals a number of extra bands which arise from vibrational state mixing occurring in the excited electronic state. The restrictive selection rules associated with vibrational coupling and with the spectroscopy of benzene allow identification of the coupled levels. The assignments of these coupled levels are presented and the modes involved in the coupled levels assessed to search for selectivity of particular modes in the coupling. It is concluded that there is no particular selectivity among the ring modes that couple to ν′₇.