INFRARED RADIO DOUBLE RESONANCE SPECTROSCOPY OF $CH_{2}Br^{1}$

$^{1}$ This research was supported by the U.S. National Science Foundation. Address of Fawzy and schwendeman: Department of Chemistry, Michigan State University, East Lansing, MI 48824.Author Institution:Pure nuclear quadrupole resonances in the ground, $v_{1}, v_{6}$, and $v_{1}+v_{5}$ vibrational states of $CH_{3} ^{74}Br$ and in the ground and $\nu_{1}$ vibrational states of $CH_{3} ^{81}Br$ have been observed in the 1-300 MHz region by applying the infrared radio frequency double resonane (IR-RF DR) technique with a stripline radio frequency sample cell outside the cavity of a semi-sealed $CO_{2}$ laser. The 9R(28) and $9R(30) ^{12}C^{14}O_{2}$ laser lines near $1085 cm^{-1}$ were used for pumping. In addition to the quadrupole hyperfine structure, $A_{1}-A_{2}$ splittings in the $\nu_{4}$ and $\nu_{1}+\nu_{6}$ vibrational states of $CH_{3} ^{79}Br$ have been observed. The center frequencies of the observed double resonance effects were determined by fitting the spectra to sums of Lorentzian lineshape functions. Quadrupole coupling constants, determined by least squares fits of experimental frequencies to frequencies calculated by direct diagnalization of the energy matrices, have been obtained for the grond, $\nu_{1}, \nu_{6}$, and $\nu_{1}+\nu_{6}$ vibrational states of $CH_{3} ^{79}Br$ and for the ground and $\nu_{1}$ vibrational states of $CH_{3} ^{81}Br$. The $\ell$-doubling constants have been determined for the $\nu_{4}$ and $\nu_{1}+\nu_{6}$ vibrational states of $CH_{3} ^{79}Br$. From the laser coincidences with the assigned transitions, the centers of $\nu_{1}$ and $\nu_{1} - v_{6}\leftarrow \nu_{6}$ vibration-rotation bands of $CH_{3} ^{79}Br$ have been estimated. The results of the present work will be compared with previous results obtained by other spectroscopic techniques