15min:

FUMIE X. SUNAHORI, RAMYA NAGARAJAN AND DENNIS J. CLOUTHIER, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055.

The boron carbide (¹¹BC and ¹⁰BC) free radical has been produced in a pulsed discharge jet using a precursor mixture of 1% trimethylborane [B(CH₃)₃] in high pressure argon. The 560 nm B ^{4 -} - X ^{4 -} electronic transition of both isotopologues has been studied in detail by LIF and emission spectroscopy. The 290 nm E ⁴ - X ^{4 -} band system was also studied using high-resolution LIF techniques, although the rotational structure of the bands was found to be quite complicated due to significant spin-spin and spin-orbit splittings in the excited state. In order to fully assign the spectra, an optical-optical double resonance (OODR) scheme was implemented in which a yellow-green dye laser beam populated a specific rotational level of the B state and a second tunable red dye laser beam was used to promote the E ⁴ - B ^{4 -} transition. The OODR transitions were detected by monitoring the resulting E ⁴ - X ^{4 -} UV fluorescence. The OODR spectra consist of readily assignable spin-split P-, Q-, and R-branch lines from a single intermediate state N value, which greatly facilitated the assignment of the E - X LIF spectra. Progress in analyzing the spectra will be discussed.