Interfacial reaction of water ice on polycrystalline vanadium and its effects on thermal desorption of water

AbstractThermal desorption experiments of Formamide (NH2CHO) and methylamine (CH3NH2) were performed in LERMA-Cergy laboratory to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces, and to understand their interaction with water ice. We found that more than 95 % of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate, and is released into the gas phase with a desorption energy distribution Edes = (7460 – 9380) K, measured with the best-fit pre-exponential factor A=1018 s-1. Whereas, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes =3850-8420 K) is measured with the best-fit pre-exponential factor A=1012s-1. A fraction of solid methylamine, of about 0.15 monolayer diffuses through the water ice surface towards the HOPG substrate, and desorbs later, with higher binding energies (5050-8420 K), which exceed that of the crystalline water ice (Edes =4930 K), calculated with the same pre-exponential factor A=1012 s-1.

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Thermal desorption of water ice in the interstellar medium

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2001.04835.x ◽

2001 ◽

Vol 327 (4) ◽

pp. 1165-1172 ◽

Cited By ~ 201

Author(s):

H. J. Fraser ◽

M. P. Collings ◽

M. R. S. McCoustra ◽

D. A. Williams

Keyword(s):

Interstellar Medium ◽

Thermal Desorption ◽

Water Ice

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Photodesorption of Water Ice from Dust Grains and Thermal Desorption of Cometary Ices Studied by the INSIDE Experiment

The Astrophysical Journal ◽

10.3847/1538-4357/ab25e7 ◽

2019 ◽

Vol 880 (1) ◽

pp. 12 ◽

Cited By ~ 6

Author(s):

Alexey Potapov ◽

Cornelia Jäger ◽

Thomas Henning

Keyword(s):

Thermal Desorption ◽

Dust Grains ◽

Water Ice

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Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731006 ◽

2018 ◽

Vol 612 ◽

pp. A47 ◽

Cited By ~ 13

Author(s):

H. Chaabouni ◽

S. Diana ◽

T. Nguyen ◽

F. Dulieu

Keyword(s):

Energy Distribution ◽

Gas Phase ◽

Thermal Desorption ◽

Binding Energies ◽

Desorption Energy ◽

Exponential Factor ◽

Water Ice ◽

Ice Surface ◽

Ice Surfaces ◽

Best Fit

Context. Formamide (NH2CHO) and methylamine (CH3NH2) are known to be the most abundant amine-containing molecules in many astrophysical environments. The presence of these molecules in the gas phase may result from thermal desorption of interstellar ices. Aims. The aim of this work is to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces and to understand their interaction with water ice. Methods. Temperature programmed desorption (TPD) experiments of formamide and methylamine ices were performed in the sub-monolayer and monolayer regimes on graphite (HOPG) and non-porous amorphous solid water (np-ASW) ice surfaces at temperatures 40–240 K. The desorption energy distributions of these two molecules were calculated from TPD measurements using a set of independent Polanyi–Wigner equations. Results. The maximum of the desorption of formamide from both graphite and ASW ice surfaces occurs at 176 K after the desorption of H2O molecules, whereas the desorption profile of methylamine depends strongly on the substrate. Solid methylamine starts to desorb below 100 K from the graphite surface. Its desorption from the water ice surface occurs after 120 K and stops during the water ice sublimation around 150 K. It continues to desorb from the graphite surface at temperatures higher than160 K. Conclusions. More than 95% of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate and is released into the gas phase with a desorption energy distribution Edes = 7460–9380 K, which is measured with the best-fit pre-exponential factor A = 1018 s−1. However, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes = 3850–8420 K) is measured with the best-fit pre-exponential factor A = 1012 s−1. A fraction of solid methylamine monolayer of roughly 0.15 diffuses through the water ice surface towards the HOPG substrate. This small amount of methylamine desorbs later with higher binding energies (5050–8420 K) that exceed that of the crystalline water ice (Edes = 4930 K), which is calculated with the same pre-exponential factor A = 1012 s−1. The best wetting ability of methylamine compared to H2O molecules makes CH3NH2 molecules a refractory species for low coverage. Other binding energies of astrophysical relevant molecules are gathered and compared, but we could not link the chemical functional groups (amino, methyl, hydroxyl, and carbonyl) with the binding energy properties. Implications of these high binding energies are discussed.

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Non-thermal desorption of complex organic molecules

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834787 ◽

2019 ◽

Vol 627 ◽

pp. A55 ◽

Cited By ~ 8

Author(s):

E. Dartois ◽

M. Chabot ◽

T. Id Barkach ◽

H. Rothard ◽

B. Augé ◽

...

Keyword(s):

Cosmic Rays ◽

Gas Phase ◽

Thermal Desorption ◽

Methyl Acetate ◽

Vacuum Ultraviolet ◽

Organic Molecules ◽

Bulk Composition ◽

Water Ice ◽

Desorption Mechanism ◽

Complex Organic

Context. The occurrence of complex organic molecules (COMs) in the gas phase at low temperature in the dense phases of the interstellar medium suggests that a non-thermal desorption mechanism is at work because otherwise, COMs should condense within a short timescale onto dust grains. Vacuum ultraviolet (VUV) photodesorption has been shown to be much less efficient for complex organic molecules, such as methanol, because mostly photoproducts are ejected. The induced photolysis competes with photodesorption for large COMs, which considerably lowers the efficiency to desorb intact molecules. Aims. We pursue an experimental work that has already shown that water molecules, the dominant ice mantle species, can be efficiently sputtered by cosmic rays. We investigate the sputtering efficiency of complex organic molecules that are observed either in the ice mantles of interstellar dense clouds directly by infrared spectroscopy (CH3OH), or that are observed in the gas phase by millimeter telescopes (CH3COOCH3) and that could be released from interstellar grain surfaces. Methods. We irradiated ice films containing complex organic molecules (methanol and methyl acetate) and water with swift heavy ions in the electronic sputtering regime. We monitored the infrared spectra of the film as well as the species released to the gas phase with a mass spectrometer. Results. We demonstrate that when methanol or methyl acetate is embedded in a water-ice mantle exposed to cosmic rays, a large portion is sputtered as an intact molecule, with a sputtering yield close to that of the main water-ice matrix. This must be even more true for the case of more volatile ice matrices, such as those that are embedded in carbon monoxide. Conclusions. Cosmic rays penetrating deep into dense clouds provide an efficient mechanism to desorb complex organic molecules. Compared to the VUV photons, which are induced by the interaction of cosmic rays, a large portion desorb as intact molecules with a proportion corresponding to the time-dependent bulk composition of the ice mantle, the latter evolving with time as a function of fluence due to the radiolysis of the bulk.

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235. Diffusive Sampling/Thermal Desorption/Mass Spectrometry Techniques for Monitoring Personal Exposures to Toxic Chemical Substances

10.3320/1.2758007 ◽

2003 ◽

Author(s):

W. Hendricks

Keyword(s):

Mass Spectrometry ◽

Thermal Desorption ◽

Diffusive Sampling ◽

Toxic Chemical ◽

Chemical Substances ◽

Desorption Mass Spectrometry ◽

Personal Exposures ◽

Toxic Chemical Substances

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Wordly Corrasions: Philology and Narrative inWorstward Ho

Journal of Beckett Studies ◽

10.3366/jobs.2017.0187 ◽

2017 ◽

Vol 26 (1) ◽

pp. 53-68

Author(s):

Mark Byron

Keyword(s):

First Principles ◽

Alexander Pope ◽

Literary Texts ◽

Water Ice ◽

Primary Documents ◽

Land Farming ◽

King James Bible ◽

A Site ◽

Thomas Browne ◽

Geological Formations

Scholarly research over the last twenty years has marked a profound shift in the understanding of Beckett's sources, his methods of composition, and his attitudes towards citation and allusion in manuscript documents and published texts. Such landmark studies as James Knowlson's biography, Damned to Fame (1996), and John Pilling's edition of the Dream Notebook (1999), and the availability of primary documents such as Beckett's reading notes at Reading and Trinity libraries, opened the way for a generation of work rethinking Beckett's textual habitus. Given this profound reappraisal of Beckett's material processes of composition, this paper seeks to show that Beckett's late prose work, Worstward Ho, represents a profound mediation on writing, self-citation, and habits of allusion to the literary canon. In its epic gestures, it reorients the heavenly aspiration of Dante's Commedia earthwards, invoking instead the language of agriculture, geology and masonry in the process of creating and decreating its imaginative space. Beckett's earthy epic invokes and erodes the first principles of narrative by way of philology as well as by means of deft reference to literary texts and images preoccupied with land, farming, and geological formations. This process is described in the word corrasion, a geological term referring to the erosion of rock by various forms of water, ice, snow and moraine. Textual excursions into philology in Worstward Ho also unearth the strata comprising Beckett's corpus (in particular Imagination Dead Imagine, The Lost Ones, and Ill Seen Ill Said), as well as the rock or canon upon which his own literary production is built. A close reading of Worstward Ho turns up a number of shrewd allusions to the King James Bible and Thomas Browne, as one might expect, but also perhaps surprisingly sustained affinities with the literary sensibilities of Alexander Pope and the poetry of S. T. Coleridge. The more one digs, the more Beckett's ‘little epic’ seems to become one of earthworks, bits of pipe, and masonry, a site and record of literary sedimentation.

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