Infrared multiphoton dissociation of acetic anhydride: Experimental study

The infrared multi‐photon dissociation (IRMPD) of acetic anhydride to generate state‐selected CH 2 has been investigated by using time and wavelength resolved fluorescence techniques. It has been observed that the generation of the nascent ground state CH 2 ( a 1 A 1 ) is delayed by about 0.6 μ relative to the onset time of the excited CH 2 ( b 1 B 1 ). The relative population of the ground and excited state CH 2 and the onset time for the appearance of the ground state CH 2 have been found to depend strongly on CO 2 laser output fluences. These results appear to have a strong bearing on the structure of the potential energy surfaces of the intermediate CH 2 CO. A possible photolysis mechanism is proposed to explain these experimental results.