Fast Heavy-Ion-Induced Anion–Molecule Reactions on the Methanol Droplet Surface

Abstract

To gain insight into complex ion−molecule reactions induced by MeV-energy heavy ion irradiation of condensed matter, we performed a mass spectrometric study of secondary ions emitted from methanol microdroplet surfaces by 2.0 MeV C 2+ . We observed positive and negative secondary ions, including fragments, clusters, and reaction products. We found that a wider variety of negative ions than positive ions (such as C 2 H − , C 2 HO − , C 2 H 5 O − , and C 2 H 3 O 2 − ) were formed. We performed measurements for deuterated methanol (CH 3 OD) droplets to identify the hydrogen elimination site of the intermediates involved in the reactions and to reveal the mechanism that generates various negative reaction product ions. Comparing the results of CH 3 OD with CH 3 OH droplets, we propose that the primary formation mechanism is association reactions of anion and neutral fragments, such as CH 3 O − + CO → C 2 H 3 O 2 − . Quantum chemical calculations confirmed that the reactions can proceed with no barrier. This study provides new insights into the importance of rapid anion−molecule reactions among fragments as the mechanism that generates complex molecular species in fast heavy-ion-induced reactions.

Mass spectrometric study of fast heavy-ion induced products on microdroplet surfaces

“…In this topical review, we present our recent advances in the experimental study of fast-ion-induced physicochemical processes in liquid systems. Mass spectrometric studies using the microdroplet technique are described for various solutions such as water, alcohol, and aqueous solutions of glycine [21][22][23][24][25][26][27]. Furthermore, we review experimental studies in which liquid microjet targets were employed [28][29][30][31][32].…”