MOLECULAR-BEAM MILLIMETER SIDE-BAND FOURIER-TRANSFORM SPECTROMETER-IIINJECTION ALONG THE CAVITY AXIS

We have recently described a molecular beam millimeter sidebands Fouri er transform spectrometer (MB-MMSBFT) (1). Basically this spectrometer makes use of a sidebands technic to move the delicate switching probl em towards the centimeter range. This brief communication, reports an enhancement of the previously described spectrometer. In the actual ve rsion the molecular sample is injected along the cavity axis instead o f perpendicular to this axis. The time spent by the molecules in the f ield is then enlarged, contributing to the enhancement in resolution. Trials have been driven with propyne and methyl cyanide, showing an ul timate linewidth of 10 kHz (HWHM) at 51 GHz.