10min:

JIANJUN YE, H. F. PANG AND A. S-C. CHEUNG, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong.

High resolution optical-optical double resonance (OODR) spectra of YCl and YBr in the spectral region between 338.9 and 371.7 nm have been obtained using laser radiation from continuous wave dye and Ti:sapphire lasers pumped by argon ion lasers. The OODR spectrum was observed by recording the laser induced fluorescence from the excited state. Reacting laser-ablated yttrium atoms, respectively, with BCl₃ and C₂H₅Br seeded in helium produced YCl and YBr molecules. For YCl, the [27.2] ¹ state was reached via the intermediate B¹ from the X¹ state. The molecular constants for the v = 1 level of the [27.2] ¹ state were determined. For YBr, two new electronic states, namely: [26.0] ¹ and [29.0] ¹ were observed via the intermediate C¹ state from the X¹ state. Accurate molecular constants for the v = 4 and 5 levels of the [26.0] ¹ state and the v = 1 and 2 of the [29.0] ¹ state were determined. The observation of the spectra of isotopic molecules confirmed the vibrational quantum number assignment of the measured vibronic levels.