Photon Stimulated Desorption from interstellar ice analogs: recent results usingsynchrotron radiation.
J.-H. Fillion,1 R. Dupuy,1R. Basalgète,1 G. Féraud,1 C. Romanzin,2 L. Philippe,1 T. Putaud,1 V.
Baglin,3 R. Cimino,4 X. Michaut,1 and M. Bertin1
1Sorbonne Université, Observatoire de Paris, Université PSL, CNRS-LERMA, Paris, France
2
Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, Orsay, France
3
CERN, Genève, Switzerland
4Laboratori Nazionali di Frascati (LNF)-INFN, Frascati, Italy

Photon Stimulated Desorption (PSD) processes play a key role in the exchanges between thegas and solid phases of cold regions of the interstellar medium, where a lot of molecules are
expected to freeze out on dust grains with the temperature forbidding their thermal escape.
These processes have been used to explained otherwise puzzling gas phase observations ofsimple molecules like CO in dense cores or cold H2O in outer parts of protoplanetary disks.
They are also invoked as ways to get complex organic molecules (COMs) presumably formedon grains into the gas phase. Second, photon-induced desorption of residual molecules
adsorbed on the cryogenic parts of accelerators such as the LHC can be a limiting factor for
their vacuum performances. Desorption rates and mechanisms, especially in the submonolayer regime, can therefore be of particular interest in this case.
I will present an approach to study PSD of condensed films of molecules of astrophysicalinterest at cryogenic temperatures, using synchrotron radiation. Recent results obtained in theVUV and soft X-ray ranges will be presented. In the VUV, we will focus on the PSD from
Amorphous Solid Water (ASW) and discuss experimental results evidencing two major
desorption mechanisms [1], [2]. Quantitative desorption yields from acetonitrile CH3CN inpure and mixed samples will be also presented [3]. In the soft X-ray range, results obtained at
the K-edge of Oxygen atoms will be discussed in the context of protoplanetary disks, first in
the case of pure H2O [4], CO [5], CH3OH [6] samples and secondly in the case H2O-rich andCO-rich samples containing CH3OH [7].
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[3]
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