Recombination of perfluoroalkyl radicals with I(5p 52P [formula omitted]), I(5p 52P [formula omitted]) atoms accompanied by radiation

Abstract

The processes of the recombination of perfluoroalkyl radicals with iodine atoms in the ground I(5p 5 2P 3 2 ) and first excited I(5p 5 2P 1 2 ) electron states accompanied by radiation, R( X )+I(5p 5 2P 1 2 )→ (M) RI( 3Q 0+, v′)→RI( X )+ hv (i), R( X )+I(5p 5 2P 3 2 )→RI( 1Q, 3Q 1; v′)→RI( X + hv (ii), have been studied by the method of quantitative laser-induced chemiluminescent kinetic spectroscopy (QLICKS). The radicals and iodine atoms were obtained in the RI photolysis at λ=266 nm. The chemiluminescence spectra in the range 700–1200 nm (i) and 1000–1200 nm (ii) and the values of the chemiluminescence rate constants k i, k ii: k i=0.6±0.15 (R=(CF 3) 3C, M=RI) to 9±3 (R=CF 3CFCF 3, M=Ar) (units, 10 −16 photon cm 3/particle 2 s); k ii > 10 −15 photon cm 3/particle 2 s, were measured. The significant k i value is a consequence of the existence of a minimum at the potential energy surface of the RI( 3Q 0+) state. The spontaneous radiationless decay RI( 3Q 0+)→RI( 1Q)→R+I( 2P 3 2 is shown to have a small (š 10 9 s −1) rate and, hence, the crossing of the 3Q 0+ and 1Q terms lies above the R+I( 2P 1 2 ) dissociation limit of RI( 3Q 0+). The recombination R+I( 2P 1 2 , 2P 3 2 can occur via the formation of the I( 2P 1 2 )M (or I( 2P 3 2 )M) complex or in the framework of the energy transfer mechanism.