Products and Reaction Sequences in Tetrahydrofuran Exposed to Low-Energy Electrons

Abstract

Electron-stimulated reactions in solid films of tetrahydrofuran (THF), condensed on Kr spacers deposited on a Pt substrate, or directly onto the substrate, were induced and monitored simultaneously with use of high-resolution electron-energy-loss spectroscopy in the ranges of vibrational and electronic excitations. The spectra of the molecular films obtained after a certain time of exposure to electrons at incident energies of 14 and 15.5 eV were analyzed and different products were identified. Besides an aldehyde, which is the main product, olefins, conjugated olefins, as well as CO were identified. Closer investigation of the reactions of propionaldehyde, as a model aldehyde, demonstrates that CO appears in THF as a secondary product (i.e., from the intermediate aldehyde). On the basis of the cross sections for the formation of an aldehyde from THF, of CO from propionaldehyde, and for the loss of propionaldehyde under electron impact, the reaction sequences were evaluated with the help of a kinetic model. This analysis suggests that some CO could also be formed directly from THF (i.e., without involvement of an intermediate aldehyde).

Absolute angle-differential elastic and vibrational excitation cross sections for electron collisions with tetrahydrofuran

“…Figure 6 shows a sample electron energy loss spectrum. It is similar to the thin-film spectrum of Lepage et al [4] and Jäggle et al [7] and the gas-phase spectrum of Milosavljević et al [14]. The individual vibrations are only partially resolved, but the consultation of the spectroscopic vibrational levels, the table of which has been given by Lepage et al [4], and of the results of routine density functional theory (DFT) normal mode calculations [32,33], reveals that various types of vibrations have their characteristic energy ranges and can be studied individually.…”

Partial cross sections for dissociative electron attachment to tetrahydrofuran reveal a dynamics-driven rich fragmentation pattern

“…The last study is of special interest here since it identified a number of core-excited resonances. Complementary to the gas phase, series of experiments with THF deposited on a surface was performed by Lepage et al [25], Antic et al [26,27], Breton et al [28], Jäggle et al [29], and Park et al [30].…”

Low-energy electron scattering by tetrahydrofuran

“…In particular, low-energy electron interactions with tetrahydrofuran (THF), the simplest model of the furanose ring that links the phosphate groups in the DNA backbone, have been studied intensively by both experimental and computational [21,[24][25][26][27][28] methods. These studies have provided valuable information about processes relevant to understanding electron transport and reactivity in biological media, including vibrational [4,8,11,15,18] and electronic excitation [3,8,11,20,22,23], dissociative attachment [5,6,10,14,19], electron trapping and reactivity in condensed THF [7,11,13], and the elastic [8,[15][16][17]20] and total scattering [9,12,21] cross sections. Although the reported measurements of the elastic electron cross section are generally consistent, there are some disagreements at higher energies; more importantly, data below 6 eV collision energy are scant, with the only reported measurements being those of Allan [15].…”