Delayed burst of particles from Ar matrices doped with CH4 and radical-radical interaction

TL;DR

This study investigates the delayed explosive desorption of particles from methane-doped argon matrices under electron irradiation, revealing the roles of radicals and charged species in the process through spectroscopic and emission measurements.

Contribution

It provides new insights into the mechanisms of delayed particle desorption involving radical interactions and nonstationary luminescence in methane-doped argon matrices.

Findings

Identification of H, CH, and C as radiation products

Observation of self-oscillations during irradiation

Role of CH3 radicals and H atoms in desorption process

Abstract

The delayed explosive desorption of particles from Ar matrices doped with methane stimulated by an electron irradiation was studied in the extended concentration range from 1% to 10% using emission spectroscopy methods. Registration of the cathodoluminescence (CL) spectra of CH4-containig Ar matrices revealed following products of radiation-induced methane transformation: H, CH and C. Three series of experiments were performed with different irradiation and heating modes: (i) continuous irradiation at low temperature with accumulation of radiolysis products, (ii) heating of the pre-irradiated films with measurements of relaxation emissions, specifically thermally stimulated exoelectron emission (TSEE) and (iii) external heating of the pre-irradiated films under beam. These measurments of the, so called, nonstationary luminescenve (NsL) at the selected wavelenghs and nonstationary desorption (NsD) in combination with TSEE registration provided an information on reactions of charged and neutral species of interest. Taking into account that the CH radical can be considered as a signature of the CH3 species [27] we obtained the information on a role of H atoms and CH3 radicals in stimulation of explosive delayed desorption of particles from Ar matrices doped with methane. Two bursts of long-period self-oscillations together with short-period ones with a limited number of periods were observeed during stationary irradiation of all methane-doped Ar matrices at low temperatures. Processes leading to the self-oscillations of particle yield are discussed.