Identification of spectrum in the charge resonance band region

Pump-probe photodepletion (hole-burning) experiments are performed on mass-selected cluster ions in the gas phase. An electronic spectrum of (C6H6)2 + in near-infrared region comprises two charge resonance bands at 920 and 1160 nm. Intensities of these two bands monitored by the probe laser are shown to be reduced by the same amount with the introduction of the pump laser. The behavior proves that the CR bands are due to two distinct transitions of a single isomer. No evidence is found for the existence of other isomers of (C6H6)2 +.