Mode selective laser chemistry of ethylene

The action of 29 rotational lines of the CO2 laser on ethylene at low pressure (1 to 2 Torr) and subsequent relaxation are investigated by means of a time of flight device, coupled to a mass spectrometer. In all cases activation is sufficient to convert ethylene efficiently into its triplet state. Two different behaviors of laser excited ethylene are discussed. They depend on which line the laser is tuned to. Considering that two IR active modes extend their rotational manifolds over the range covered by CO2 laser radiations (ν7 and ν10), it is believed that the different laser lines energize selectively either one of them.