Knowledge Bank

The Stark effect of the $22-21(E1)$ and $21-30(E1)$ microwave transition in the ground state and the $22-21(E1)$ microwave transition in the first excited C-O stretching vibrational state were measured by means of infrared-microwave double resonance method with the 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 $CO2$-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 $Dab$ 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 $|\mu a|/D$ &$0.8957\pm 0.0005$ &$0.9213\pm 0.0008$\ $|\mu b|/D$ &$1.40\backslash a\backslash a\pm 0.02$ &$1.39\backslash a\backslash a\pm 0.09$\ $|Dab|/$MHz &$71.9\backslash a\backslash a\pm 1.5$ &$347\backslash a\backslash a\backslash a\pm 27$\ \hline \end{tabular} \end{table} The frequency of the infrared transition was obtained to be lower by $125\pm 2$ MHz than that of the $P(34)CO2$ laser at 9.4$\mu m$