Storage ring measurements of the dissociative recombination rate of rotationally cold H 3 +

Abstract

A review. We present dissociative recombination measurements, using the CRYRING ion storage ring, of H+3 ions produced in a supersonic expansion discharge source. Before and after the CRYRING measurements, the ion source was characterized in Berkeley using IR cavity ringdown spectroscopy, and was found to exhibit a typical rotational temp. of ∼30 K. Our measurement of the dissociative recombination cross section using this ion source revealed resonances that had not been obsd. clearly in previous expts. that used rotationally hot ion sources. Based on the present measurements, we infer a thermal dissociative recombination rate coeff. for ions at interstellar temps. of ∼ 2.6 × 10-7 cm3 s-1. Our results are in general agreement with theor. calcns. of the dissociative recombination cross section by Kokoouline and Greene. We will review the enigma of the abundance of H+3 in the diffuse interstellar medium, and discuss the impact of these expts., esp. in the context of the recent observation of H+3 towards ζ Persei. [on SciFinder(R)]