IR LASER SIDEBAND OBSERVATIONS IN GEH4 AND CD4

We have used the technique of IR laser sideband spectroscopy to observe single ro-vibrational transitions in the ν2 fundamental of GeH4. The isotope structure has been resolved within the Doppler width of the lines. The isotopic frequency shift for the J″=7 transition in the R branch of ν2 was found to be 120 MHz/amu. This value is much smaller than the isotope shift in the ν4 fundamental (0.22 cm-1=6.5 GHz/amu) which has been observed with a conventional high resolution grating spectrometer. For GeH4 a line width (FWHM) of 44.4 MHz was found which compares well with the Doppler width (41 MHz) at 300 K. The application of this spectroscopic method was extended to some transitions in the ν4 fundamental of CD4. In total 32 transitions have been observed in GeH4 and 17 in CD4. The absolute accuracy in frequency measurement is ±60 MHz. © 1979 American Institute of Physics.