HIGH RESOLUTION IR SPECTROSCOPY OF MONOHALOCARBENES: THE CH STRETCH FUNDAMENTAL AND VIBRATIONAL COUPLING IN HCF

We present first results from high-resolution infrared study of jet-cooled singlet monofluorocarbene (HCF) in the CH stretch region near 2600~cm$^{-1}$. Fully rotationally resolved absorption spectra of the CH stretch ($\nub{1}$) fundamental band, the $\nub{1}$+$\nub{3}$ $\leftarrow$ $\nub{3}$ hot band, and part of the $\nub{2}$+$\nub{3}$ combination band are observed and analyzed, representing first experimental determination of rovibrational constants for these upper/lower levels. Transitions accessing each of the $\nub{1}$ $K_a'$ = 0, 1 and 2 manifolds are observed, with clear evidence for strong rovibrational coupling between the $\nub{1}$ $K_a'$ = 2 and $\nub{2}$+$\nub{3}$ $K_a'$ = 3 manifolds and allowing for perturbation analysis of a c-type Coriolis interaction between these two levels. The inclusion of such Coriolis coupling explains the large perturbations in both line positions and intensities observed for $K_a'$ = 2 and 3 subbands of the $\nub{1}$ and $\nub{2}$+$\nub{3}$ rovibrational bands, respectively. The results are in good agreement with, and also significantly extend, the analyses from previous studies of HCF using stimulated emission pumping from the first electronically excited state