Sub-Doppler spectroscopy of mixed state levels in CH2

Perturbations in the 7(16) and 8(18) mixed singlet/triplet levels of (a) over tilde (1)A(1) (0,0,0) methylene, CH2, have been reinvestigated by frequency-modulated laser sub-Doppler saturation spectroscopy. The hyperfine structure was completely resolved for both the predominantly singlet and the predominantly triplet components of these mixed rotational levels using (b) over tilde B-1(1)-(a) over tilde (1)A(1) optical transitions near 12 200 cm(-1) with megahertz resolution. The mixing coefficients were obtained from the observed hyperfine splittings and a two-level deperturbation model. The analysis also determines the energy separation of the unperturbed zero-order levels and the unperturbed hyperfine splittings for the triplet perturbing levels 6(15) (H) over tilde B-3(1) (0,3,0) and 9(37) (X) over tilde B-3(1) (0,2,0). (C) 2010 American Institute of Physics. [doi:10.1063/1.3502084]