Knowledge Bank

Infrared-microwave two-photon spectra in the $980cm-1$ region have been obtained for the asymmetric tip molecule $CD2CO$. The radiation sources are a $CO2/N2O$ cw laser and backward wave oscillators operating in the 8-18 GHz region. The microwave radiation is amplified to $\sim$20 watts by means of a traveling wave tube amplifier. The microwave frequency is stepped and the spectrum is recorded by a laboratory computer. Two-photon transitions have been observed for the $\nu 4$ and $\nu 6$ bands of $CD2CO$. Initial assignments were based on the results of an infrared laser Stark $study.1$ The $\nu 6$ two-photon transitions have been observed in a sample cell outside the laser cavity. The $\nu 4$ transitions are considerably weaker and were observed with an in-cavity cell. A computer program has been implemented for theoretical calculation of the intensities of infrared-microwave two-photon transitions for an asymmetric top molecule. The calculation is complicated by the existence of many possible intermediate states and by the necessity of many summations over M components. The computational procedure will be described briefly. $\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}$This work was supported by the National Science $Foundation.1$D. Coffey, JR., C. Yamada, and E. Hirota, J. Mol. Spectrosc. 64, 98-108 (1977).