Fourier transform dispersed fluorescence spectroscopy: Observation of new vibrational levels in the 5000–8000 cm−1 region of ã 1A1 CH2

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Abstract
Dispersed fluorescence spectra from the CH2 b̃ 1B1 state to highly excited vibrational levels of the ã 1A1 state were recorded by a new technique, Fourier transform dispersed fluorescence spectroscopy. The spectra obtained clearly show the advantages of using a Fourier transform spectrometer for dispersing fluorescence, namely emission over a wide spectral range can be efficiently detected with high sensitivity and resolution. These advantages allow four new vibrational levels in the CH2 ã 1A1 state to be observed; the (2,0,0) and (0,5,0) vibrational overtones and the (1,2,0) and (1,3,0) combination bands. The vibrational term values for these levels are given, along with the harmonic frequencies and anharmonicities for the v1 and v2 modes. From the (0,5,0) term value an improved estimate of the barrier height to linearity in the CH2 ã 1A1 state is made.