Infrared-microwave double resonance spectroscopy of GeH4

Abstract
The highly sensitive method of infrared‐microwave double resonance in a laser cavity has been used to observe the distortion‐induced rotational spectrum for the ground vibrational state of GeH4. Coincidences between the (ν2, ν4) fundamental vibration–rotation bands and infrared laser lines (CO2, isotopic CO2, and N2O) were used for detection of the very weak rotational transitions. Four resonances with J=18 and one resonance with J=11 were assigned. The frequencies of these resonances give accurate information on the quartic, sextic, and octic tensor distortion coefficients of GeH4.