Knowledge Bank

Optical double resonance measurements of several rovibronic transitions in the $b~1B1\leftarrow a~1A1$ origin band of CH$2$ were reported at the 2008 Symposium., paper WG03, 63rd OSU International Symposium on Molecular Spectroscopy.} Although these assignments are unambiguous, the data are sparse and the spectral resolution was limited by the pulsed laser used. We have therefore recorded the complete absorption spectrum between approximately 8200 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and 8400 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ at Doppler-limited resolution using an extended cavity diode laser source. This region includes the expected positions of both the $Ka=0\leftarrow 1$ and $Ka=1\leftarrow 0$ subbands. Although the calculated intensities for these transtions are small,, J. Molec. Struct. \textbf{517-8} 247 (2000).} the observed spectra have good signal-to-noise ratio and many additional transitions are seen. We have assigned all the expected transitions involving $Ka\prime =0$, and part of the subband with $Ka\prime =1$. However definitive assignment of transitions involving $J\prime$ = 4 and higher in the second subband have so far eluded us, and additional optical double resonance measurements are needed to decide between several possible assignments. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Support from the Department of Energy Faculty and Student Teams Program for Bloomsburg University is gratefully acknowledged.