Gas-phase kinetics are reported for the reactions of Ti(a3F) with 0 2 , N20, NO, CO,, S02, and NO2 from 300 to 600 K. Titanium atoms were produced by the photolysis of T i c 4 at 248 nm and were detected by laserinduced fluorescence. Arrhenius expressions obtained for these reactions at a buffer gas pressure of 20 Torr are k(O2) = (1.69 f 0.41) X exp(-(14.3 f 0.9 kJ/mol)/RTcm3 s-l, k(N0) = 3.28 f 0.69) X exp(-(3.62 f 0.71 kJ/mol)/RT) cm3 s-l, k(CO2) = (7.0 f 1.6) X exp(-(2.66 f 0.64 kJ/mol)/RT) cm3 s-l. The rate constant of Ti with NO2 was found to be temperature independent from 300 to 500 K with a value of (9 f 4) X cm3 s-l. Quoted uncertainities are f2u. With the exception of Ti + 0 2 , all reactions were investigated as a function of pressure. Only the reactions of Ti with NO and C02 were found to depend on the argon buffer gas pressure. Termolecular rate constants at 300 Kweredeterminedtobe(5.8 f 2.6) X 10-31cm6s-1 and(3.5 f 1.0) X 10-32cm6s-1 forNOandCO2,respectively. exp(-(11.6 f 0.8 kJ/mol)/RT) cm3 s-l, k(N2O) = (1.74 f 0.44) X exp(-(14.9 f 0.8 kJ/mol)/RT) cm3 s-l, and k(SO2) = (1.70 f 0.33) X
The gas-phase reactivities of W(a 5D,, a 7S3) with O2 in the temperature range 298-573 K are reported. Tungsten atoms were produced by the photodissociation of W(CO), and detected by laser-induced fluorescence. The disappearance rate constant of the s1d5 a ' S , state is of the order of the gas kinetic rate constant. The removal rate constants for the s2d4 a 5D, states are J dependent. The a 5D, states are not as reactive as the s1d5 a 'S3 state and are found to be temperature dependent. The disappearance rates of all states in the presence of O2 are found to be pressure independent with buffer gas. Physical quenching rate constants for the excited states in the presence of Ar, He, N, and sF6 are also reported. Results are discussed in terms of the different electron configurations of the states.
Articles you may be interested inThe effect of incident spinorbit state on the chemiluminescent reactions of Ba(3 D J ) with several oxidants J. Chem. Phys. 85, 4453 (1986); 10.1063/1.451766 Spinorbit effects in chemical reactions: The reaction of spinorbit stateselected Ca(3 P 0 J ) with Cl2, Br2, and CH3Cl J. Chem. Phys. 81, 2375 (1984); 10.1063/1.447937 Effect of atomic spinorbit state on reactivity: Reaction of stateselected Ca(3 P 0 J ) with Cl2 A study of the reactions Ca(1 S,3 P 0, and 1 D)+N2O under singlecollision conditions and at higher pressures: Chemiluminescence cross sections, photon yields, and collisional energy transfer in CaO* by N2O J. Chem. Phys. 74, 6178 (1981); 10.1063/1.441008Direct determination of individual reaction cross sections for the two spinorbit states Ar+(2 P 3/2, 2 P 1/2) The dependence of the chemiluminescence cross section on initial spin-orbit level has been measured for the reaction of metastable Ca( 4s4p 3 P~) with C1 2 , CH 3 Br, CH 2 Br 2 , CH 2 ~ CHCH 2 ;Sr, and C 6 H 5 CH 2 Br, using an optical pumping state selection technique. Optical pumpIng depletIon was also used to determine what fraction of the chemiluminescence was due to the second metastable Ca( 4s3d In) level present in the incident atomic beam. Chemiluminescence cross sections for both the 3 po and In reactions were separately determined' tot~ attenuation and intramul~iplet. mixing cross secti~ns were also estimated. The Ca( 3 P 0) spin~ orbtt dependence for the chemIlumInescence channel In all the reactions studied was substantial and 0: ~im~lar magnitud 7 , with an order of reactivity J = 2> J = 1 > J = O. This spin-orbit sel~ctlVlty IS relate~ to dIfferences in the evolution of the asymptotic spin-orbit states onto the vanous electrostatIc surfaces at smaller separations. It is remarkable that this selectivity persists with polyatomic reagents.4s4p 3p O and 4s3d In (see Fig. 1), both of which are produced in our discharge atomic beam source. 46 Previously, the I D /3 pO population ratio was estimated to be small (0;;;5%), so that chemiluminescence from In reactions were judged to be negligible if the corresponding 3 pO reaction was exothermic. This population ratio was calculated from the 4332
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