Dissociative Excitation of Acetylene Induced by Electron Impact: Excitation-emission Cross-sections

Abstract

The optical emission spectrum of acetylene excited by monoenergetic electrons was studied in the range 190-660 nm. The dissociative excitation and dissociative ionisation associated with excitation of the ions initiated by electron impact were dominant processes contributing to the spectrum. The spectrum was dominated by the atomic lines (hydrogen Balmer series, carbon) and molecular bands (CH(A-X), CH(B-X), CH + (B-A), and C2).Besides the discrete transitions we have detected the continuum emission radiation of ethynyl radical C2H(A-X). For most important lines and bands of the spectrum we have measured absolute excitation-emission cross sections and determined the energy thresholds of the particular dissociative channels.

Diagnostics of Collisions between Electrons and Water Molecules in Near-ultraviolet and Visible Wavelengths

“…The experiments were carried out using a crossed-beam apparatus using distilled and deionized water. The apparatus is described in detail in previous publications (Danko et al 2013;Országh et al 2017) and is briefly described here. The electron beam generated by an electron gun crosses perpendicularly with a molecular beam formed by an effusive capillary in the vacuum chamber.…”

Dissociative Excitation of Nitromethane Induced by Electron Impact in the Ultraviolet – Visible Spectrum

“…The measurements were performed on the electron induced fluorescence apparatus at Comenius University Bratislava, previously described in [14,15]. In short, the device (Figure 1) consists of a vacuum chamber with background pressures typically below 10 -8 mbar.…”

“…The transitions from higher levels were too weak, blended with the background noise, and were therefore not detected in our spectrum. The lifetime of hydrogen states increases with increasing excitation level, up to several microseconds for the Hd and above (Table 1, [15]). That allows a significant portion of excited atoms to leave the apparatus' field of view before emitting photon, further decreasing the intensity of the lines associated with transitions higher levels.…”

“…Interestingly, no other atomic emission lines were detected in our spectra. For example, in the spectrum of acetylene (C2H2) measured at the same electron impact energy of 50 eV, both C I and C II lines are clearly visible [15].…”

Electron Induced Emission of Nitrous Oxide in the UV-VIS Spectral Range

“…The experimental apparatus used for this study was described in detail in [15][16][17]. A simple scheme of the device is shown in the figure 1.…”