Tag: ta2.13

22-EPN3-107: Characterising the electron-impact-induced emission of CS2 to constrain sulfur abundances in cometary and planetary atmospheres

Visit by Steven Bromley, Auburn University (USA), to TA2 Facility 13 – Electron Induced Fluorescence Laboratory (Slovakia).
Dates of visit: 08 – 19 May 2023

The main goals of the 2023 visit were to study the electron impact emission cross sections, spectral features, and dissociation thresholds of CS₂ gas. The products of CS₂ – atomic sulfur and its ions, CS, excited CS₂, and CS₂⁺ – make CS₂ a rich target of inquiry. Further, the products CS and atomic S are routinely observed in near-nucleus observations of comets (see e.g. discussion in Noonan et al. 2023). Measurements of sulfur abundances in comets show discrepancies between remote and in-situ observations, and improved electron-impact data for CS₂ may help resolve this discrepancy. The present experiments are part of a long-term campaign to understand diagnostic electron-impact driven emission and ionization of diatomic/polyatomic molecules in cometary atmospheres. We expect these data will provide valuable insights in one of our ongoing projects to investigate sulfur abundances through analyses of 100+ archived comet observations. In the first week of our visit to the EIF lab, we measured the electron-impact spectrum of CS₂ gas at various electron energies between 0 – 100 eV, with energies chosen based on known thresholds for CS, CS₂⁺, and atomic fragment production. During this time, we also began developing an emission model for CS in order to simplify the future analyses of these data. In the second week of the visit, higher-resolution spectra and several cross sections were measured in order to begin comparisons to existing literature. We also identified, for the first time, the emissions of atomic fragments (S I, S II) in the near-infrared red-ward of 600 nm.

21-EPN-FT1-023: Diagnostics of electron collisions with small organic molecules present in the atmospheres of small bodies and planets

Visit by Bartosz Michalczuk, Siedlce University (Poland), to TA2 Facility 13 – Electron Induced Fluorescence Laboratory (Slovakia).
Dates of visit: 21 – 30 November 2022

Report Summary:

The main objective of the project was to study electron impact processes of small organic compounds, using acetone as the first target.

• Record and analyse emission spectra of acetone induced by electron impact at several different energies in the range 10 – 100 eV.
• Determine emission cross sections corresponding to selected most intensive transitions in range of impact energies (from the thresholds of selected process to 100 eV).
• Identify neutral products of electron impact fragmentation of acetone.
• Determine reaction kinetics parameters such as threshold energies for selected electron impact excitation reactions of acetone.

During the first half of the visit, we measured electron-impact spectra of acetone at multiple electron energies and generated partial spectral electron energy map which provides the spectral information at various electron energies and thus the efficiency curves (relative emission cross-section curves).
During the second half of the visit, the measured data was partially analysed. The emission band in the range of 415 – 445 nm corresponds to the radiation of CH (A²Δ–X²Π) (ν,ν) fragment. Less intensive radiation of CH (B²Σ−–X²Π) (0,0) fragment was identified within 386 – 402 nm. Several emission lines of hydrogen’s Balmer series Hγ – Hη were detected throughout the spectrum as well. Individual rotational transitions from P, Q, R branches of both CH fragments were identified according to LIFBASE 2.1.1 spectroscopy tool, which is software to chart the spectroscopy of diatomic molecules. The rotational temperature of the LIFBASE spectrum was set to ~ 5000 K.

Read the full scientific report, with kind permission by Steve Bromley.