Abstract
Singlet methylene has been produced in its lowest rotational states by photolysis of jet-cooled ketene at photolysis wavelengths near threshold, and the laser-induced fluorescence excitation spectrum has been recorded from 16 170 to 18 250 cm -1 . The spectral simplification obtained has allowed identification of several previously unknown vibrational bands in the upper state. Three of the new bands are assigned as combination bands involving the ν 1 vibration of the b ̃ state; they should allow a more accutate determination of this mode's frequency and anharmonic constants. The variations in intensity with photolysis wavelength and the photolysis energy thresholds determined by photofragment excitation spectra for selected transitions permit unambiguous assignments of the lower states. The techniques presented here provide important tools for dealing with this congested and highly perturbed spectrum. © 1989.