Keywords: astrochemistry, interaction, mass spectrometry Internship Duration: 30/11/-1 - 30/11/-1
Head of the hosting team: Anne LAFOSSE
Website: Click here
Address of the host laboratory: Orsay Institute for Molecular Sciences (ISMO) Team SIM2D - Electrons-solids bât. 520, rue André Rivière 91405 ORSAY France
Supervisor 1: LAFOSSEE-mail: anne.lafosse@universite-paris-saclay.fr Phone: +33 1 69 15 76 98
Supervisor 2: AMIAUD
In the interstellar medium (ISM), molecular ices form on the surface of dust grains and are submitted to radiations. The resulting modifications include enrichment in new organic compounds and radiation-stimulated desorption, which may explain the molecular abundances observed in the gas phase. A major contribution to these chemical changes is due to the secondary electrons generated in the ice by the primary radiations. The progress of ISM observations, in particular thanks to the JWST space telescope, is pushing astrochemical model developments, in order to improve the representation of these non-thermal desorption processes. In this internship, the aim is to measure the electron-induced desorption efficiencies, at high or low energies (10 eV to 500 eV), from different pure or mixed ices, notably acetonitrile, methane and formaldehyde. The method consists in depositing ices at 23 K under ultra-high vacuum and irradiating them with electrons at known energy and flux. Thermal or non-thermal desorption of the neutral molecular species is detected by mass spectrometry. The chemical composition of the ice is analysed by vibrational spectroscopy. Quantities such as effective desorption cross-sections and desorption efficiencies (in molecules per electron) are determined after careful data treatment. These quantities are compared with available photo-desorption rates and literature references.
Mass spectrometry (QMS) for Temperature Programmed Desorption (TPD) and Electron Stimulated Desorption (ESD) analysis Vibrational spectroscopy : HIgh Resolution Electron Energy Loss Spectroscopy (HREELS)
Cryogenic Chemistry and Quantitative Non-Thermal Desorption from Pure Methanol Ices: High-Energy Electron versus X-Ray Induced Processes, D. Torres-Díaz et al. ChemPhysChem n/a, no n/a. Consulté le 3 février 2023. https://doi.org/10.1002/cphc.202200912
