The spectrum of CH2 near 1.36 and 0.92 microm: reevaluation of rotational level structure and perturbations in a(010).

The spectrum of methylene in the 1.3-1.4 and 0.89-0.94 microm wavelength regions has been recorded in absorption using frequency-modulated cw diode and Ti:sapphire laser sources. The spectral lines have Doppler-limited resolution and have been assigned to bands in the b(1)B1 <-- a(1)A1 electronic spectrum of the radical. In three of the four bands studied, the lower state is the bend excited, v2" = 1, level of the a state and two of the upper levels lie below the energy of the degenerate linear configuration of the b/a pair. Together with previously measured data pertaining to v2" = 1, the data have been used to refine the precision of the experimentally determined rotational structure in this level. Although several K" = 1 levels do show shifts of more than 0.1-0.2 cm(-1), multiple strong perturbations due to near-resonant background X(3)B1 rovibrational levels, such as are known to occur in the a(1)A1, v2" = 0 level have not been found in v2" = 1. Absorption lines due to the predominantly triplet X(040) 4(14) level, responsible for most of the perturbation of a(010) 5(15), have been identified in the spectra. The data also fix the energies of the b(0,0,0)2, a(0,7,0)1, b(0,2,0)3, and a(0,10,0)2 upper vibronic levels, where the numbers in parentheses are the vibrational quantum numbers with superscript K, the projection of the total angular momentum on the a-inertial axis.