Interaction of low-energy electrons with dimethyl sulfide and dimethyl disulfide

Abstract

We report elastic integral cross sections for low-energy electron scattering by gas-phase dimethyl sulfide and dimethyl disulfide, obtained with the Schwinger multichannel method with pseudopotentials. Our symmetryresolved cross sections for dimethyl sulfide reveal that the single broad structure at 3.25 eV observed in the electron transmission spectrum (assigned as a σ * CS shape resonance) would actually arise from two superimposed anion states in the B 2 and A 1 symmetry components of the C 2v point group. We also obtained two low-lying shape resonances for dimethyl disulfide, in good agreement with the available electron transmission data. In view of the recently reported measurements on dissociative electron attachment to dimethyl disulfide [C. Matias, A. Mauracher, P. Scheier, P. Limão-Vieira, and S. Denifl, Chem. Phys. Lett. 605-606, 71 (2014)], we also calculated cross sections for stretched S-S bond lengths, which indicate a fast stabilization consistent with the experimental data.

Recent advances in the application of the Schwinger multichannel method with pseudopotentials to electron-molecule collisions

“…The π * 1 , π * 2 and the σ * anion states have significant probabilities on the C=S group. The latter results are also consistent with the recent calculations for dimethyl-disulfide [117], a prototype system to model the sulfide bridges that take part in the stabilization of the secondary structure of proteins. In this case, the S-S bond gives rise to a resonance with a strongly repulsive potential surface, which in turn leads to the cleavage within the Franck-Condon region of the S-S stretch mode of the neutral species.…”

Electron driven processes in sulphur containing compounds CH3SCH3 and CH3SSCH3

“…Taking into account the ETS data [28] we can ascribe the high energy feature to shape resonance involving S-S antibonding state. The low energy structures lie slightly below the theoretically (resonance of σ SS * character at 0.8 eV [27]) as well as experimentally (σ SS * resonance at 1.04 eV [28]) predicted resonances. On the other hand, assuming that formation of the S − anion is accompanied by the release of the CH 3 SCH 3 molecule as a neutral counterpart the thermodynamic threshold is 0.3 eV, which is in reasonable good agreement with the experimental data.…”

“…Indeed, a VUV photoabsorption experiment on CH 3 SCH 3 provides an evidence for the existence of the core excited resonance at 6.348 eV, which is a result of the excitation to an antibonding orbital along the sulphur lone pair electrons (n S → σ*) of the CH 3 SCH 3 molecule [26]. Furthermore, recent theoretical calculations predict the existence of high lying shape resonances at energy around 5.8 eV for CH 3 SCH 3 and around 7 eV for CH 3 SSCH 3 [27]. The energy of these theoretically predicted resonances matches quite well the peaks maxima from our experiments.…”

“…The peaks in the high energy range can be easily attributed to core excited resonances (valence or Rydberg states) by comparison of their maxima with the high resolution VUV photo-absorption spectra [26]. The origin of the low energy peak is not obvious since, from electron transmission spectroscopy (ETS), the lowest shape resonance of σ SC * character has been observed at 3.25 eV [25] and theory predicts the resonance of B 2 symmetry at 2.6 eV [27].…”

Electron interaction with dimethyl disulfide in the low- and intermediate-energy range

“…On the theoretical side, two investigations on electron scattering by DMDS appeared recently in the literature. In 2014, Santos et al [5] reported a study of electron interaction with DMDS at incident energies up to 12 eV using the Schwinger multichannel method (SMC).…”