Oxidation reaction of the ground state Si atom was studied by using a crossed molecular beam technique at 13.0 kJ/mol of collision energy. The Si atomic beam was generated by laser vaporization and crossed with the oxygen molecular beam at right angle. Products at the crossing region were detected by the laser-induced fluorescence (LIF). The LIF of SiO(A 1 Pi-X 1 Sigma+) was used to determine the vibrational state distribution of the electronic ground state, SiO(X 1 Sigma+). The determined distribution was inverted with the maximum population at v"=4, and in good agreement with the recent quasiclassical trajectory calculation on the singlet potential energy surface. The agreement suggested that an abstraction mechanism is dominant at the collision energy studied here. One of the counterproducts, O(3PJ), was also observed by the vacuum ultraviolet LIF and the distribution of the spin-orbit levels were determined. The formation of O(3PJ) was consistent with the significant population of v"=7 and 8 states of SiO, which could be explained by the presence of the triplet product channel with higher exothermicity.

The dynamics of the reaction, V(a 4FJ)+NO-->VO(X 4Sigma-)+N was studied by using a crossed-beam technique at 16.4 kJ/mol of collision energy. The V atomic beam was generated by laser vaporization and crossed with the O2 beam at a right angle. The laser-induced fluorescence (LIF) for the transition of VO(B 4Pi-X 4Sigma) was used to determine the rotational state distribution of the reaction product in the vibrational ground state. Almost pure V(a 4FJ) beam was obtained by using the mixture of NH3 with N2 as a carrier gas. Comparing the LIF spectra of VO measured for two carrier gases, i.e., NH3N2 and pure N2, it was concluded that the vibrational ground state of VO(X 4Sigma-) is formed almost entirely from the reaction of V(a 4FJ) and the contribution of the metastable V(a 6DJ) is negligible. The observed rotational distribution was similar to a statistical prior prediction, and suggested that the title reaction proceeds via a long-lived intermediate, which is consistent with an electron transfer mechanism.

Oxidation reactions of the gas-phase titanium atom in its excited state with oxygen molecule, Ti(a(5)F(J)) + O(2) --> TiO(A(3)Phi,B(3)Pi) + O, were studied by a crossed-beam technique. Metastable excited Ti, Ti(a(5)F(J)), was generated by an optical pumping method and the reaction products were detected by the chemiluminescence spectroscopy. The chemiluminescence from TiO(A(3)Phi,B(3)Pi) was analyzed to determine vib-rotational state distributions of both excited states and their branching ratio. The vib-rotational state distribution of TiO(B) was represented by the statistical energy disposal and the branching ratio of TiO(A)/TiO(B) was also consistent with the statistical expectation. These results suggested the presence of long-lived intermediates in the course of the reactions of the excited Ti(a(5)F(J)) atom with O(2). Also observed was the significant deviation of the vibrational state distribution of TiO(A) from the statistical one and another reaction pathway which may not proceed via the long-lived intermediates was implied.