Collisional redistribution of vibrational energy in CO2‐laser‐excited benzene

We have monitored changes in the population of benzene vibrational levels during and after irradiation with an intense CO2‐laser pulse. Our method was to induce fluorescence from the first excited singlet state (1B2u) by absorption of tunable ultraviolet radiation. By varying the delay time between the infrared and ultraviolet pulses and by employing ultraviolet frequencies within many bands of the 1A1g–1B2u system, we measured the temporal evolution of the vibrational energy distribution over 12 benzene levels. We also used the technique to assign bands of the ultraviolet absorption spectrum that involve vibrational levels pumped by the infrared laser.

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