Ternary Recombination of H₃⁺ and D₃⁺ with Electrons in He–H₂ (D₂) Plasmas at Temperatures from 50 to 300 K

Abstract

We present results of plasma afterglow experiments on ternary electron-ion recombination rate coefficients of H3(+) and D3(+) ions at temperatures from 50 to 300 K and compare them to possible three-body reaction mechanisms. Resonant electron capture into H3* Rydberg states is likely to be the first step in the ternary recombination, rather than third-body-assisted capture. Subsequent interactions of the Rydberg molecules with ambient neutral and charged particles provide the rate-limiting step that completes the recombination. A semiquantitative model is proposed that reconciles several previously discrepant experimental observations. A rigorous treatment of the problem will require additional theoretical work and experimental investigations.

Low temperature rates for key steps of interstellar gas-phase water formation

“…Most studies in flow tubes and drift chambers are carried out at helium pressures around 1 torr, resulting in densities on the order of 10 16 cm −3 , at least three orders of magnitude higher than in the present work. For some critical reactions (that have a long-lived collision complex), high number densities can influence the rate coefficients significantly; for example, the electron recombination of H 3 + in flow tubes seems to be dominated by ternary effects ( 38 , 39 ). However, in the present case, one would probably expect that collisions with helium would stabilize the collision complex and increase the rate coefficient rather than decrease it.…”

State selective study of H3+recombination in Cryo-FALP and SA-CRDS experiments at 77 K

“…Measured ternary recombination rate coefficients also showed pronounced nuclear spin specificity at temperatures 100-200 K. Theory of the aforementioned ternary processes is based on a calculation of the life time of rotationaly excited neutral p/o H 3 Rydberg molecule. This molecule is formed in collision of p/o H + 3 with electron [18][19][20] and theory predicts the order of magnitude of the ternary rate coefficient correctly. However, the theory is not detailed enough for closer comparison with the experimental values of state selected ternary rate coefficients and their temperature dependencies.…”

“…The technical details were described elsewhere [14,20,25], only very short description will be given here. A source of parastate-enriched hydrogen gas (para-hydrogen generator) was also described in our previous publication [12].…”

“…[14][15][16][17] and references therein. In studies of binary recombination of H + 3 ions in He/Ar/H 2 gas mixture it was observed that the decay of afterglow plasma is dependent on He number density [5,6,[18][19][20]. This indicates that a ternary He-assisted recombination process contributes to the overall recombination in afterglow plasma in He/Ar/H 2 gas mixture:…”

Three-body mechanisms in plasma recombination of H3+and D3+Ions

“…The question then is: What was wrong with Leu's data? The situation became clearer as a result of the systematic afterglow work by the Prague group [3,5]. It was found that the effective recombination rate coefficient has two parts, a binary and a three-body (ternary) part so that…”