KINETICS OF DEPLETION OF ELECTRONICALLY EXCITED TI ATOM BY CH4, C2H2, C2H4 AND C2H6

The kinetics of depletion of ground state Ti(a(3)F) and electronically excited state Ti(a(5)F) upon interactions with CH4, C2H2, C2H4, and C2H6 are studied in a fast-flow reactor at a He pressure of 0.70 Torr. No depletion of ground state Ti(a(3)F) was observed upon interaction with all hydrocarbons studied here. Two alkanes, CH4 and C2H6, were also quite inert for depletion of the excited state Ti(a(5)F). On the other hand, C2H2 and C2H4 deplete the excited state Ti(a(5)F) very efficiently. Rate constants were determined to be (266 +/- 86) and (476 +/- 88) x 10(-12) cm(3)s(-1) for Ti(a(5)F) + C2H4 and Ti(a(5)F) + C2H2, respectively. These large rate constants compared with the ground state Ti were explained by an electron donor-acceptor interaction model that works in the interaction between C2H4 or C2H2 and the excited state with unfilled 4s orbital.