Infrared absorption spectroscopy of D<SUB>3</SUB>: an investigation of the formation mechanisms of triatomic hydrogen species<BR><P>

Professor T Amano<BR>
Institute for Astrophysics and Planetary Sciences, Ibaraki University, 2-1-1 Bunks, Milo 310-8512, Japan<BR><P>

The visible and infrared emission spectra of H<SUB>3</SUB> and D<SUB>3</SUB> were discovered by Herberg and co-workers in the cathode glow of liquid nitrogen cooled hollow cathode discharges.  We observed the 3s 2A11-3p  2E1 (36000 cm<SUP>-1</SUP> band) and 3d-3p 2E1(3950 cm<SUP>-1</SUP> band) transitions of D<SUB>3</SUB> in absorption with a difference frequency laser as a radiation source.  The D<SUB>3</SUB> radical was generated by 10 kHz AC discharges of D2 gas at a pressure of about 400 mTorr in a hollow cathode discharge cell cooled with either methanol at 213 K or liquid nitrogen at 77 K.  It was found that the coolant temperature had little effect on the spectra and most of the spectra were recorded using methanol cooling.  The lifetimes of the states involved in these bands were significantly shorter than the collision intervals under the present experimental conditions, and the observed lineshapes exhibited a broad non-thermal velocity distribution which carried pertinent information on the formation mechanism of D<SUB>3</SUB> and the dissociative recombination of D<SUB>3</SUB><SUP>+</SUP>.