A LONG PATH-LENGTH PULSED SLIT VALVE APPROPRIATE FOR HIGH-TEMPERATUREOPERATION - INFRARED-SPECTROSCOPY OF JET-COOLED LARGE WATER CLUSTERS AND NUCLEOTIDE BASES

We report the design and performance of a pulsed slit valve for genera tion of supersonically cooled species in a long path length planar exp ansion. Utilizing three commercial solenoids driven synchronously by a n economic power transistor circuit, the valve produces pulses adjusta ble in width from 500 to 1000 mu s with a repetition rate up to 80 Hz. The pulsed valve can be operated continuously for 12 h, and operation over one month is typical before major maintenance is required. The p ath length X density product attained by this pulsed source is suffici ent for observing large cluster species, such as the water hexamer, on our far-infrared spectrometer. With the addition of a detachable samp le oven, it can also be heated up to 230 degrees C to inject nonvolati le molecules into planar supersonic expansions. (C) 1996 American Inst itute of Physics.