Electron transmission spectroscopy: Resonances in triatomic molecules and hydrocarbons

Abstract

Compound states of triatomic molecules and simple hydrocarbons are studied using electron transmission spectroscopy. Structures in the derivative of the current transmitted through a gas-filled collision chamber are interpreted as resonances in the electron-molecule cross sections. At low electron energies (0–6 eV) we observe, in N2O, H2S, and C2H4, broad and featureless structures which we identify as shape resonances. In the same energy range, the molecules CO2, NO2, C6H6, and SO2 exhibit narrow structures which form vibrational progressions. In CO2, NO2, and C6H6, these vibrational progressions are identified as shape resonances; in SO2, the interpretation is not clear cut. No low-energy resonances are observed in H2O and in CH4. At higher energies (9–17 eV) we observe sharp structures for H2O, H2S, N2O, CO2, and C2H4 (but not for C6H6 and CH4). These structures form bands, each band consisting of a vibrational progression. The states which are responsible for the bands consist of two Rydberg electrons moving in the field of a particular positive-ion core. These bands are similar to those found previously in diatomic molecules.

Theoretical total cross sections fore-SO2scattering over a wide energy range (0.1−2000 eV) revealing a 3.4-eV shape resonance

“…which coincides with the observation of a resonance. Such a resonance was first observed by Sanche and Schulz [11] and subsequently confirmed by the measurements of Simon et al [12] and Andric et al [13] who showed the temporary formation of the SO 2 − state which decays into vibrational excitation of the neutral. Andric et al [13] further confirmed that the symmetry of this state was most likely 2 B 2 with the Gianturco et al [15]; (short dot line) Natalense et al [16]; (dash-dotdot line) Gupta and Baluja [14]; (dash-dot line), Machado et al [17]; (dotted line) Shi et al [19]; (bold short dashed line) Raj and Tomar [20].…”

“…The other notable fact is that although e-SO 2 has been studied over a wide range of impact energies, all of the previous groups have carried out work over a limited range of impact energies. The present work is therefore unique as we have investigated the total cross section over a wide energy range starting from 0.1 eV to a high energy of 2000 eV, and we are able to detect the resonance at 3.4 eV as predicted by Sanche and Schulz [11] and confirmed by Simon et al and Andric et al [12,13]. Similarly we are able to theoretically confirm the shape resonance at 5.1 eV as detected by Gulley and Buckman [6].…”

“…Thus reviewing previous work on e-SO 2 scattering it is notable that there are more experimental data [6][7][8][9][10][11]13,17] than theoretical investigations [11,12,14,15,17]. The other notable fact is that although e-SO 2 has been studied over a wide range of impact energies, all of the previous groups have carried out work over a limited range of impact energies.…”

“…Zubek et al [7], Szmytkowski and Maciag [8], and Szmytkowski et al [9] * minaxivinod@yahoo.co.in have employed linear transmission experiments to measure total cross sections for incident energies 1.5-7 eV, 1.5-70 eV, and 6-370 eV, respectively, while Sokolov and Sokolova [10] measured total cross sections employing the electron cyclotron resonance technique in the energy range 1.5-10 eV. Sanche and Schulz [11] performed an electron transmission experiment to detect resonance structure in SO 2 , identifying a broad shape resonance at 3.4 eV. This was subsequently confirmed by the measurements of Simon et al [12] and Andric et al [13], which showed the formation of a temporary SO 2 − state which decays to leave the molecule excited in one of its vibrational modes.…”

Electron-induced chemistry of alcohols

“…The electron affinity of the parent Rydberg state is of the order of 0.3-0.5 eV for the s 2 configuration. [26][27][28][29]31 Read expressed the relation with a modified Rydberg-Ritz formula. 32 Spence 33 fitted a linear relationship between the energy of the Feshbach resonance E F and the first ionization energy I, E F = A Á I + B, for many hydrogen-and methyl halides.…”