Identification of absorption lines in gases used to modulate the CO<inf>2</inf>laser

The absorption lines in methyl bromide, vinyl chloride, and 1, 1 difluoroethylene used to modulate the CO2laser lines have been spectroscopically observed using a spectrometer which uses the signal generated by mixing a CO2laser and a millimeter wave klystron in a gallium arsenide loaded waveguide as a source. The results indicate that Stark modulation with symmetric top molecules is not necessarily due to large first-order splittings as previously assumed and that the modulation is not linear with the applied electric field.