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Keywords:

cf2((a)over-tilde b-3(1)), oxygen-atoms, tetrafluoroethylene, kinetics, photodissociation, hydrocarbons, cf2(3b1), emission, o-2, cf, Science & Technology, Physical Sciences, Chemistry, Physical, Physics, Atomic, Molecular & Chemical, Chemistry, Physics, CF2((A)OVER-TILDE B-3(1)), OXYGEN-ATOMS, TETRAFLUOROETHYLENE, KINETICS, PHOTODISSOCIATION, HYDROCARBONS, CF2(3B1), EMISSION, O-2, CF, 02 Physical Sciences, 03 Chemical Sciences, 09 Engineering, Chemical Physics, 34 Chemical sciences, 40 Engineering, 51 Physical sciences

Abstract:

The rate coefficients of the removal of metastable electronically excited CF2((a)B-3(1)) by several hydrocarbons have been determined for the first time over an extended temperature range (295 K-550 K). CF2(B-3(1)) radicals were generated by pulsed laser photolysis Of C2F4 at 193 nm and real-time pseudo-first-order decays of the relative CF2(B-3(1)) concentration were obtained by monitoring the CF2(B-3(1) --> (1)A(1)) emission at 570-700 nm. Over the experimental temperature range, the rate coefficients of CF2 ((a)B-3(1)) removal by (di-)alkenes exhibited a marked negative temperature dependence: k(C3)H(6)(T) = (7.8+/-2.3) x 10(-13) exp[+(500 +/- 100)K /T] cm(3) S-1 molecule(-1), k(iso-C4)H(8)(T) = (1.4+/-0.2) x 10-(12) exp[+(762+/-36)K/T] cm(3) s(-1) molecule(-1), k(C3H4)(T) = (2.1+/-0,5) x 10(-13) exp[+(790+/-83)K/T] cm(3) s(-1) molecule(-1). For the removal of CF2 ((a)B-3(1)) by C3H8, the rate coefficient exhibited a small positive temperature dependence: k(C3H8)(T) = (6.5+/-2.2) x 10(-13) exp[-(252+/-130)K/T] cm(3) s(-1) molecule.