15min:

ZHEN-DONG SUN, QIANG LIU, Department of Physical Sciences, University of New Brunswick, Saint John, NB, Canada E2L 4L5; VLADIMIR DOROVSKIKH, M. YU. TRETYAKOV, Department of Physical Sciences, University of New Brunswick, Saint John, NB, Canada E2L 4L5, Permanent address: Institute of Applied Physics, Nizhny Novgorod, Russia 603950; R. M. LEES AND LI-HONG XU, Department of Physical Sciences, University of New Brunswick, Saint John, NB, Canada E2L 4L5.

A broadband tunable CO₂-laser/microwave sideband spectrometer is now in operation at UNBSJ with the following noteworthy features: (i) The source coverage has been significantly improved as we have obtained useful sideband power for regular CO₂ lines up to very high J (J_max = 56) as well as hot and sequence band CO₂ laser lines, giving continuous coverage over significant spectral regions; (ii) The whole system has now been automated with sophisticated computer-controlled sweep and data capture in which the HP-MW synthesizer and Fabry-Perot etalon filter are scanned simultaneously to give wide-band continuous sweep over the full 7-18 GHz range for either sideband; (iii) Balanced detection of sample and reference has greatly improved the S/N ratio through compensation for background variations. Tests on the dense methanol spectrum in our room temperature multipass static cell around 10 µm have shown excellent resolution and S/N ratio using the hot and sequence band CO₂ lines. Use of the source in the first tests of our supersonic slit-jet cooled molecular beam with OCS have shown significantly reduced line width compared to room-temperature static-cell values.