Knowledge Bank

The near-infrared spectrum of $CH2(b~1B1-a~1A1)$ was observed using frequency-modulated diode laser absorption spectroscopy. Rovibronic transitions between $11038cm-1$ 4 and $11370cm-1$ were assigned based on the known lower state combination differences. On the basis of comparison with published results of quantum chemical calculations including the Renner-Teller effect, three upper rovibronic levels were assigned possessing both $a~$ and $b~$ primary electronic wavefunction character: $K=1b~(0,2,0)$, $K=1a~(1,7,0)$, and $K=4b~(0,2,0)$. Transitions involving J as high as 8 were observed in $K=1b~(0,2,0)$. In addition to further characterizing the $CH2$ bending potential surfaces near the barrier lo linearity, the analysis also extends the rotational number of ground state levels that are accurately known.