Real time study of the infrared multiphoton dissociation of vinylbromide

The infrared multiphoton dissociation of vinylbromide has been study in real time by the analysis of the spontaneous luminescence emitted in the dissociation process and by laser induced fluorescence of C-2 and CH species. It has been found that, although the dissociation of vinylbrumide is a non-collisional process, formation of C-2 and CH takes place through a collisional process in the presence of the infrared laser field. Laser induced fluorescence excitation spectra of C-2 demonstrate that it is formed vibrationally hot in the ground state, its vibrational temperature estimated to be 2200 +/- 200 K. The addition of Ar increases the dissociation yield of vinylbromide by a rotational hole filling effect but, for pressures higher than 12 hPa, the production of excited C2(d(3)Pi(g),) is strongly quenched. These experiments have shown also that, in the ground state, approximately five times more population is formed vibrorotationally excited than in the nu" = 0 level, not depending on the fluence of the laser pulses. C2H2, HBr and H-2 are found as final products for fluences of 170 J/cm(2). For fluences of approximately 300 J/cm(2) diacetylene and a solid black soot are also formed. (C) 1999 Elsevier Science S.A. All rights reserved.