Reactions of sulfurated ions in thermal plasmas and reaction dynamics by gas-phase infrared emission spectroscopy.

摘要

A Selected Ion Flow Tube (SIFT) was employed to study more than 110 ion/molecule reactions with emphasis on sulfurated ions important to the chemical evolution of interstellar molecular clouds (ISC), planetary atmospheres, and other plasmas. These studies have greatly extended the data base on gas-phase reactivity of sulfurated ions. A Flowing Afterglow (FA) also was used to investigate the dynamics of ionic reactions by emission spectroscopy in the ultraviolet-visible (UV-VIS) and near-infrared (IR) spectral regions. For the IR region, a new detection system was developed and adapted to an existing FA apparatus. A modulation technique developed for signal discrimination in the IR experiments was also adapted to the identification of source reactions of chemiluminescence in the UV-VIS experiments.;Survey studies of the reactions of S+, S2 +, SO+, O2+, and CS + with many neutral molecules of interstellar interest were performed with a SIFT. General features of the reactivities of these ions were elucidated, and it was determined from the reactions of S+, SO+ and S2+ that the HS2 (thiosulfeno) and HSO (thioperoxy) radicals are likely to be important interstellar species. Further SIFT studies with the HSSH+ and HSOH+ ions permitted the thermokinetic bracketing of the proton affinities of HS 2 and HSO for the first time.;Development of the IR detection system involved the design of collecting optics, signal discrimination and modulation techniques, and the adaptation of FA/spectroscopic facilities to detecting infrared signals from ionic reactions. The new system was tested with the well-studied reactions H + Cl2, H + NO2, and N(2D) + H2, as well as the ionic reaction H + Cl-. Emission from vibrationally-excited HF in a recombining plasma containing H3+ and SF 6- as the dominant charge carriers was interpreted as the first observed IR chemiluminescence from an ion/ion recombination.;Energy disposal in charge transfer reactions of various atomic and diatomic ions (i.e., Ar+, Cl+, N+, N 2+, and O+) with the sulfurated molecules H2S, OCS and CS2 were studied in a FA by UV-VIS emission spectroscopy. Such reactions are of fundamental interest to the elucidation of the dynamics of ion/molecule reactions.