Primary processes in the photolysis of n-butane with 8.4 and 10.0 eV photons

Abstract

The photolysis of n-C 4D 10 has been investigated with 8.4 eV and 10.0 eV photons, using HI to scavenge free radicals through the reaction: R d + HI → R d H + I (where R d is a fully deuterated alkyl or alkenyl radical). From the results of such experiments, the quantum yields of the molecular and radical products are obtained over a pressure range from 3 to 47 Torr at both energies. In addition, the photolysis of CD 3CH 2CH 2CD 3 and CD 3CD 2CH 2CH 3 have been investigated in the presence of radical scavengers over a range of pressures at both energies. The results are discussed with particular emphasis on deriving the quantum yields of all the primary processes, and following changes in the quantum yields as a function of energy. Major conclusions are: (a) the quantum yield of the process (C 4D 10 → C 4D 8 + D 2) diminishes from 0.70 to 0.37 when the photon energy is increased from 8.4 to 10.0 eV; (b) the relative overall importance of direct CC bond cleavage processes, alkane elimination processes, and D-atom elimination processes do not change significantly as a function of energy; (c) processes involving breakage of the 2, 3 CC bond strongly predominate over processes involving the 1, 2 CC bond at both energies, although there is a lower probability for localization of the energy in the center bond when the energy is increased.