(2)PI-(X)OVER-TILDE(2)SIGMA(+) ELECTRONIC BANDS OF TITANIUM METHYLIDYNE, TICH, NEAR 725 NM WAVELENGTH

Electronic bands assigned to the linear TiCH and TiCD radicals have be en recorded by laser-induced fluorescence in the 610-725 nm wavelength region, following the reaction of laser-ablated Ti atoms with methane under supersonic jet-cooled molecular beam conditions. Rotational ana lyses of high-resolution spectra have given the ground state substitut ion structure X(2) Sigma(+): r(g)(C-H) = 1.085 +/- 0.002 Angstrom: r(g )(Ti-C) = 1.7277 +/- 0.0003 Angstrom. The electronic upper state appea rs to be a very strongly perturbed (2) Pi start, with many extra rotat ional and vibrational levels appearing; it has nor barn possible to ma ke vibrational assignments, though the Omega' values have been establi shed for some of the levels. Wavelength-resolved fluorescence spectra have given two of the three ground state vibrational frequencies: TiCH : nu(2)(bend) = 578 cm(-1), nu(3)(Ti-C stretch) = 855 cm(-1) TiCD: nu( 2) = 442 cm(-1), nu(3) = 815 cm(-1) Vibrationally forbidden transition s to the ground state bending fundamental appear prominently in many o f these spectra, as a result of strong vibronic coupling. No evidence for nu(1)(pi) (the C-Il stretching vibration) has been found. (C) 1997 Academic Press, Inc.