Formation of H₃⁺ in Collisions of H₂⁺ with H₂ Studied in a Guided Ion Beam Instrument

Abstract

In order to study collisions between ions and neutrals, a new Guided Ion Beam (GIB) apparatus, called NOVion, has been assembled and tested. The primary purpose of this instrument is to measure absolute cross sections at energies relevant for technical or inter‐ and circumstellar plasmas. New and improved results are presented for forming H3+ in collisions of H2+ with H2. Between 0.1 eV and 2 eV, our measured effective cross sections are in good overall agreement with most previous measurements. However, at higher energies, our results do not show the steep decline, recommended in the standard literature. After critical evaluation of all experimental and theoretical data, a new analytical function is proposed, describing properly the dependence of the title reaction on the collision energy up to 10 eV.

The H2+ + HD reaction at low collision energies: H3+/H2D+ branching ratio and product-kinetic-energy distributions

“…26 and references therein). This reaction closely follows Langevin-capture behaviour for reactions with a dominant ion-induced-dipole long-range interaction, [24][25][26][27][28] and only significantly deviates from this behaviour at elevated temperatures 29 or at temperatures much below 1 K. 25,30 The reaction is strongly exothermic, with a 0 K reaction internal energy . 33,34 With this reaction, we have recently demonstrated that the ion-heating effects of stray electric fields can be strongly reduced if the ion is replaced by the parent neutral species excited to a high Rydberg state.…”

Understanding the temperatures of H3+ and H2 in diffuse interstellar sightlines

“…The results are in very good agreement with the previous measurements [27] conducted at somewhat higher energies. A recommended fit to the overall cross section can be found in [25], yielding values at low temperature that are slightly higher than the corresponding values derived from the classical Langevin collision rate. We have converted this cross section to a thermal rate coefficient…”

“…1) has been studied for many years by various experimental techniques. A recent compilation of the results can be found in [25]. Particularly noteworthy is a recent study that employs excited Rydberg molecules in a merged beams approach to reach collision energies between 5 − 60 K [26].…”

Roadmap on dynamics of molecules and clusters in the gas phase

“…The development of radiofrequency (RF) multipolar ion guides has led to guided ion-beam (GIB) setups where collisions with neutral targets take place in a scattering cell. This experimental arrangement permits to measure cross sections that are more informative on the reactive process than measurements of thermally averaged rate coefficients [84]. It should be noted at this point that an alternative way to trap ions for gas-phase molecular dynamics study is by electrostatic ion-beam traps, as detailed in Sect.…”