INFRARED-MICROWAVE DOUBLE RESONANCE OF $^{12}CH_{3}OH$ WITH A $CO_{2}$ LASER
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Date
1981
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Ohio State University
Abstract
The Stark effect of the $2_{2}-2_{1}(E_{1})$ and $2_{1}-3_{0}(E_{1})$ microwave transition in the ground state and the $2_{2}-2_{1}(E_{1})$ microwave transition in the first excited C-O stretching vibrational state were measured by means of infrared-microwave double resonance method with the $^{q}Q_{1}(2)E_{1}$ infrared transition as the pump transition in the range of 1000 V/cm to 2300 V/cm. A parallel-plate absorption cell was placed inside a $CO_{2}$-laser cavity. The plates were separated with four precision metal gauge blocks whose nominal thickness was 10 mm. The double resonance signal was observed as a change in the output power of the IR-laser, as the frequency of microwave was swept with the electric field strength at a suitable value. The dipole moment $\mu_{a}$ and $\mu_{b}$ as well as the off-diagonal rotational constant $D_{ab}$ were determined for both the ground and the excited states: [FIGURE] \begin{table}[h] \def \a{\hphantom{0}} \begin{tabular}{lll} &Gnd state &Exc state\\ \hline $|\mu_{a}|/D$ &$0.8957\pm 0.0005$ &$0.9213\pm 0.0008$\\ $|\mu_{b}|/D$ &$1.40\a\a\pm 0.02$ &$1.39\a\a\pm 0.09$\\ $|D_{ab}|/$MHz &$71.9\a\a\pm 1.5$ &$347\a\a\a \pm 27$\\ \hline \end{tabular} \end{table} The frequency of the $^{q}Q_{1}(2)E_{1}$ infrared transition was obtained to be lower by $125\pm 2$ MHz than that of the $P(34) CO_{2}$ laser at 9.4${\mu m}$
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