Nuclear spin dependence of the reaction of H3+ with H2. II. Experimental measurements
Abstract
The nuclear spin dependence of the chemical reaction H_3^+ + H2 → H2 + H_3^+ has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H_3^+ (o-H_3^+ and p-H_3^+) in hydrogenic plasmas of varying para-H2 (p-H2) enrichment. The ratio of the rates of the proton hop (kH) and hydrogen exchange (kE) reactions α ≡ kH/kE is inferred from the observed p-H_3^+ fraction as a function of p-H2 fraction using steady-state chemical models. Measurements have been performed both in uncooled (Tkin ∼ 350 K) and in liquid-nitrogen-cooled (Tkin ∼ 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of α has been found to decrease from 1.6 ± 0.1 at 350 K to 0.5 ± 0.1 at 135 K.
- Publication:
-
Journal of Chemical Physics
- Pub Date:
- May 2011
- DOI:
- Bibcode:
- 2011JChPh.134s4311C
- Keywords:
-
- chemical exchanges;
- hydrogen ions;
- hydrogen neutral molecules;
- infrared spectra;
- ion-molecule reactions;
- plasma chemistry;
- rotational states;
- 82.30.Fi;
- 33.20.Ea;
- 82.30.Hk;
- 82.33.Xj;
- 33.15.Mt;
- Ion-molecule ion-ion and charge-transfer reactions;
- Infrared spectra;
- Chemical exchanges;
- Plasma reactions;
- Rotation vibration and vibration-rotation constants