THE ELECTRONIC SPECTRUM OF TANTALUM METHYLIDYNE, TaCH

$^{*}$ Present address: School of Chemistry, University of Sydney, Building P11, Sydney, N. S. W. 2006. Australia.Author Institution: Department of Chemistry, University of British ColumbiaTantalum methylidyne, TaCH, has been produced in a supersonic free jet expansion in helium by the reaction between laser ablated tantalum and methan e. TaCD has been made similarly using $CD_{4}$. Pulsed dye laser excitation spectra from the $\Omega=0 (\tilde{X}\Sigma^{+}$) state of TaCH have been assigned to two electronic transitions whose upper states have $\Omega=0^{+}$ which proably is $^{3}\Pi$, and $\Omega=1$. The (0,0) bands of these states lie at 15638.6 cm $^{-1}$ and 16398.3 cm $^{-1}$, respectively. Wavelength resolved fluorescence emission from the $\Omega=O^{+}$ excited state has revealed a low lying $\Omega=1$ electronic state $3620 cm^{-1}$ above the ground state; this appears to be a $^{3}\Delta$ state. Two of the $\tilde{X}$ state vibrational fundamentals have been determined for TaCH(TaCD): $\nu_{2}=641(492)$ cm $^{-1}$ and $\nu_{3} = 955(910)$ cm $^{-1}$. The values determined for the $a^{3}\Delta_{t}$ state were $\nu_{2}= 606(449)$ cm $^{-1}$ and $\nu_{3} = 925(864)$ cm $^{-1}$. High resolution spectra are being recorded for selected bands; these will allow the molecular structure and the spectroscopic parameters to be detedmined accurately. The magnetic and quadrupolar hyperfine structure of $^{181}$Ta is fully resolved in the high resolution study