Tunable laser excitation followed by observation of infrared fluorescence provides a means of readily studying electronically excited photoproducts and their reactions. A number of specific examples involving the production of I*(52P1/2) and Br*(42P1 c 2 ) upon molecular photodissociation are considered. The quantum yield of I * production from HgIz is obtained as a function of wavelength. An inconclusive search was made for unobserved states in IBr which lead to I* product atoms and for states of BrCl which lead to Br*. Photodissociation of CHJz in an intense laser field is observed to undergo multiphoton dissociation. Quenching and reactive collisions of Br* and I* with halogens, I t , Br, and CI2, and interhalogens, IBr, ICI and BrCI, are investigated. Electronically adiabatic reactive channels are detected for the collisions I * + Brz -f IBr + Br* and I* + IBr + I2 -t Br*. Vibrationally excited HBr product molecules are observed in 10 "/, of the quenching collisions of Br* with H2S.

Articles you may be interested inLaser determinations of ''hot band'' quantum yields: Br*(2 P 1/2) formation in the continuum absorption of Br2 at 510-550 nm Relative quantum yield of I*(2 P 1/2) in the tunable laser UV photodissociation of iC3F7I and nC3F7I: Effect of temperature and exciplex emission J. Chem. Phys. 79, 2687 (1983); 10.1063/1.446173Quenching and reactions of laserexcited I(52 P 1/2) atoms with halogen and interhalogen molecules J. Chem. Phys. 69, 641 (1978); 10.1063/1.436629Collisional quenching of excited iodine atoms I(5p 5 2 P 1/2) by selected molecules Tunable laser, infrared fluorescence techniques are used to study the detailed photodissociation dynamics of the linear triatomic molecule HgI 2 . The quantum yield of excited I(S2p'12) atoms has been measured in the first long wavelength absorption band of Hgl2 from 265 to 320 nm. From quantitative measurements of the yield of excited I atoms, it is shown that the total absorption cross section in this region is actually composed of two distinct components. These components correspond to states leading to both excited and ground state 1 atoms according to the processes HgI 2 '!.':.,HgI+I or 1*. From the time decay of the excited 1* atoms as a function of HgI2 pressure. the collisional deactivation rate of 1* by the parent HgI2 molecule has been obtained. This quenching rate constant is 4.5±0.2X 10-10 cm 3 molecule-' s-' at T = 453 K, which is essentially a gas kinetic rate.

Articles you may be interested inConservation of the Kr+(2 P 1/2) state in the reactive quenching of Kr(5s′[1/2]0) atoms by halogencontaining molecules Rate constants for the collisional deactivation of spin--orbit excited 1(5 2 pI/2) atoms with the halogens 1 2 , Br CI 2 and interhalogens IBr, ICI, and BrCl have been determined using laser-excited, time-resolved 2', 3 -1 -1 infrared fluorescence techniques. The measured rate constants are (cm molecule ·sec ) 3.1 ±0.5XlO-ll , 5.2±0.3xW-II , 1.7±0.2XlO-12 , 6.6±0.3XlO-ll , 2.3±0.2XlO-lI , and 2.7±0.2 XIO-II , respectively. These results are discussed in terms of a collision complex formation model in which reactivetype collisions may predominate in the deactivation process under investigation. An excited Br* product is observed in the reactive collision systems 1*+Br2--+IBr+Br* and 1*+IBr--+1 2 +Br*. With an appropriate analysis of the kinetics involved, the fractions of the total deactivation rate constants attributed to these reactive channels are \5%±5% and \3%±5%, respectively.