ROTATIONAL AND TRANSLATIONAL TEMPERATURE OF SiO+ IONS PRODUCED BY LASER ABLATION OF Si IN OXYGEN GAS Yukari Matsuo*, Tohru Kobayashi*, Takashi Nakajima#, and Michio Takami* *The Institute of Phsical and Chemical Research (RIKEN), Saitama 351-0198, Japan #Institute of Advanced Energy, Kyoto University, Kyoto 611-0011, Japan We have studied laser-induced fluorescence spectra of SiO+ produced by laser ablation of a Si sample in oxygen ambient gas. The rotational temperature determined from the relative intensities of rotationally-resolved lines shows rapid thermalization toward room temperature within 20 us. The translational temperature is analyzed from the Doppler width of spectral lines, indidating relatively slow thermarization in the order of 100 us.