MECHANISM OF FORMATION OF C2* d3Пg STATE FROM CHCIF2 BY IRRADIATION WITH INTENSE IR LASER

Electronically excited radicals C2* were formed from CHC1F2 molecules by irradiation with a TEA CO2 laser. Six bands of Swan system have been observed. The mechanism of the formation of C2*d3Πg state in the infrared multiphoton dissociation of CHC1F2 is presented based on the potential energy curves of the C2 molecule. C2 is a somewhat unnsual molecule, the state b3∑g- crosses the first excited state a3Πu at an internuclear distance of about 1.80?, and lies below it for greater nuclear separations. At first, the state b3∑g- is formed in the elementary step C + CF2 + M→C2* + F2 + M of the reactionsof the photoproducts of CHC1F2 in preference to the low-lying X1∑g+ and a3Πu states, and then undergoes a radiationless transition into the d3Πg state through crossing with the d3Πg,ν′= 6 level.