Js. Shin et al., FLUENCE AND PRESSURE EFFECTS ON IR MULTIPHOTON DISSOCIATION OF ETHYLBROMIDE, Journal of photochemistry and photobiology. A, Chemistry, 84(2), 1994, pp. 105-112
The IR multiphoton dissociation of C2H5Br was studied as a function of
the laser fluence and substrate pressure using a pulsed TEA CO2 laser
at the 10P(20) (10.59 mum, 944 cm-1) laser line. The effects of added
H-2, He, N2 and NO were also studied. The reaction products were foun
d to be C2H2, C2H4, C2H6 and CH4. The increase in the partial pressure
of the products with increasing substrate pressure was interpreted in
terms of the large contribution from a collision-induced reaction bet
ween the reactant molecules excited below the reaction threshold. At a
focal fluence of less than 100 J cm-2, C2H4 was the only reaction pro
duct detected, whereas C2H2 and CH4 also appeared at higher fluence. T
he formation of C2H2 and CH4 at higher fluence was attributed to addit
ional laser photon absorption by vibrationally excited ethylene (C2H4
) primarily in the quasi-continuum state. The production of C2H6 was d
ue to C-Br bond fission. The observed dissociation data were compared
with the theoretical predictions obtained using the energy-grained mas
ter equation.