VISIBLE LUMINESCENCE STUDY OF THE INFRARED MULTIPHOTON DISSOCIATION OF 2-CHLOROETHENYLSILANE

The infrared multiphoton dissociation of 2-chloroethenylsilane induced by a tunable CO2 laser, under both collision-free and collisional con ditions, results in an intense visible luminescence. Spectral analysis of this emission was carried out, and a broad, structureless band, ce ntred at about 650 nm, was obtained. The intensity of this luminescenc e was studied in relation to multiphoton dissociation as a function of the gas pressure and the frequency and fluence of the laser beam. Lif etime measurements of the luminescence were performed for different pr essures of the parent molecule, and the radiative decay time was found to be 480 +/- 20 ns. The quenching rate of this emission by homogeneo us collisions is (1.44 +/- 0.08) x 10(-10) cm(3) molecule(-1) s(-1). T he luminescence was assigned to decay from the B-1(1) electronic state to the (1)A(1) ground state of silylene formed within the laser pulse . The detection of silylene supports the previously postulated reactio n pathways in the infrared multiphoton dissociation of 2-chloroethenyl silane. It also suggests that, at high fluence conditions, the chloroe thene elimination channel dominates the dissociation reaction. (C) 199 7 Elsevier Science S.A.