Interaction of D2 with H2O amorphous ice studied by temperature-programed desorption experiments

Amiaud, L.; Fillion, J.-H.; Baouche, S.; Dulieu, F.; Momeni, A.; Lemaire, J. L.

doi:10.1063/1.2168446

Cited by 91 publications

(171 citation statements)

References 58 publications

Supporting

Mentioning

161

Contrasting

Order By: Relevance

“…The quality of the fit is as good as in the results obtained previously. 19 The curves (c) and (d) of Fig.6 are fits from a 8-ML porous ASW sample irradiated with 256 and 448 minutes of D-atoms respectively. The experimental data were simulated by scaling down the number of accessible sites on the ice with irradiation time.…”

Section: Discussionmentioning

confidence: 99%

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Accolla

Congiu

Dulieu

et al. 2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The morphology of water ice in the interstellar medium is still an open question. Although accretion of gaseous water could not be the only possible origin of the observed icy mantles covering dust grains in cold molecular clouds, it is well known that water accreted from the gas phase on surfaces kept at 10 K forms ice films that exhibit a very high porosity. It is also known that in the dark clouds H2 formation occurs on the icy surface of dust grains and that part of the energy (4.48 eV) released when adsorbed atoms react to form H2 is deposited in the ice. The experimental study described in the present work focuses on how relevant changes of the ice morphology result from atomic hydrogen exposure and subsequent recombination. Using the temperature-programmed desorption (TPD) technique and a method of inversion analysis of TPD spectra, we show that there is an exponential decrease in the porosity of the amorphous water ice sample following D-atom irradiation. This decrease is inversely proportional to the thickness of the ice and has a value of φ0 = 2 × 10 16 D-atoms cm -2 per layer of H2O. We also use a model which confirms that the binding sites on the porous ice are destroyed regardless of their energy depth, and that the reduction of the porosity corresponds in fact to a reduction of the effective area. This reduction appears to be compatible with the fraction of D 2 formation energy transferred to the porous ice network. Under interstellar conditions, this effect is likely to be efficient and, together with other compaction processes, provides a good argument to believe that interstellar ice is amorphous and non-porous. 1.IntroductionAmorphous solid water (ASW) is reputed to be the most abundant form of water in the Universe, thanks to its propensity for forming, molecule after molecule, as a deposit on interstellar dust particles. 1,2 The accretion of icy mantles (predominantly constituted by ASW) on silicate and carbonaceous dust grains takes place in interstellar molecular clouds. Some of them are cold (~10 K) and dense (10 4 -10 6 cm -3 ) regions where gaseous species heavier than hydrogen and helium freeze out onto the grains. Beside H2O and CO, other species constitute the inventory of icy mantles such as CO2, CH3OH, CH4, H2CO and NH3, 3,4 as a result of the gasgrain interactions occurring on the surface of interstellar dust. The most important and abundant molecular species as well, H2, is formed likewise thanks to reactions occurring on amorphous water ice in molecular clouds 5,6 . In addition, a significant fraction of the gas phase species is constituted by atomic hydrogen whose abundance is mostly governed by the destruction of H2 due to cosmic rays. It has been evaluated that, in dense clouds, the average number density ratio of atomic hydrogen component compared to the molecular one is ~ 0.1%. 7 In a dark cloud, atomic hydrogen thus represents the third most abundant gas-phase species, after H2 and He.Along with atoms and molecules available in the gas-phase and the condensed/adsorbed speci...

show abstract

Section: Discussionmentioning

confidence: 99%

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Accolla

Congiu

Dulieu

et al. 2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…1), which is described elsewhere (Amiaud et al 2006;Congiu et al 2012). The set-up is dedicated to investigating physical chemical reactions on surfaces of astrophysical interest, under conditions roughly similar to those encountered in the ISM.…”

Section: Methodsmentioning

confidence: 99%

CO₂formation on interstellar dust grains: a detailed study of the barrier of the CO + O channel

Minissale

Congiu

Manicó

et al. 2013

A&A

Self Cite

View full text Add to dashboard Cite

Context. The formation of carbon dioxide in quiescent regions of molecular clouds has not yet been fully understood, even though CO 2 is one of the most abundant species in interstellar ices. Aims. CO 2 formation is studied via oxidation of CO molecules on cold surfaces under conditions close to those encountered in quiescent molecular clouds. Methods. Carbon monoxide and oxygen atoms are codeposited using two differentially pumped beam lines on two different surfaces (amorphous water ice or oxydized graphite) held at given temperatures between 10 and 60 K. The products are probed via mass spectroscopy by using the temperature-programmed desorption technique. Results. We show that the reaction CO + O can form carbon dioxide in solid phase with an efficiency that depends on the temperature of the surface. The activation barrier for the reaction, based on modelling results, is estimated to be in the range of 780−475 K/k b . Our model also allows us to distinguish the mechanisms (Eley Rideal or Langmuir-Hinshelwood) at play in different temperature regimes. Our results suggest that competition between CO 2 formation via CO + O and other surface reactions of O is a key factor in the yields of CO 2 obtained experimentally. Conclusions. CO 2 can be formed by the CO + O reaction on cold surfaces via processes that mimic carbon dioxide formation in the interstellar medium. Astrophysically, the presence of CO 2 in quiescent molecular clouds could be explained by the reaction CO + O occurring on interstellar dust grains.

show abstract

“…3.2) were performed in Cergy-Pontoise using the FORMOLISM experimental set-up (Amiaud et al 2006). Briefly, the apparatus consists of an ultra-high vacuum stainless steel chamber, with base pressure in the low 10 −10 mbar range, containing an amorphous silicate-coated gold surface (5−400 K) Fig.…”

Section: Methodsmentioning

confidence: 99%

The desorption of H₂CO from interstellar grains analogues

Noble

Theulé

Mispelaer

et al. 2012

A&A

Self Cite

View full text Add to dashboard Cite

Context. Much of the formaldehyde (H 2 CO) is formed from the hydrogenation of CO on interstellar dust grains, and is released in the gas phase in hot core regions. Radio-astronomical observations in these regions are directly related to its desorption from grains. Aims. We study experimentally the thermal desorption of H 2 CO from bare silicate surfaces, from water ice surfaces and from bulk water ice in order to model its desorption from interstellar grains. Methods. Temperature-programmed desorption experiments, monitored by mass spectrometry, and Fourier transform infrared spectroscopy are performed in the laboratory to determine the thermal desorption energies in: (i.) the multilayer regime where H 2 CO is bound to other H 2 CO molecules; (ii.) the submonolayer regime where H 2 CO is bound on top of a water ice surface; (iii.) the mixed submonolayer regime where H 2 CO is bound to a silicate surface; and (iv.) the multilayer regime in water ice, where H 2 CO is embedded within a H 2 O matrix. Results. In the submonolayer regime, we find the zeroth-order desorption kinetic parameters ν 0 = 10 28 mol cm −2 s −1 and E = 31.0 +/− 0.9 kJ mol −1 for desorption from an olivine surface. The zeroth-order desorption kinetic parameters are ν 0 = 10 28 mol cm −2 s −1 and E = 27.1 +/− 0.5 kJ mol −1 for desorption from a water ice surface in the submonolayer regime. In a H 2 CO:H 2 O mixture, the desorption is in competition with the H 2 CO + H 2 O reaction, which produces polyoxymethylene, the polymer of H 2 CO. This polymerization reaction prevents the volcano desorption and co-desorption from happening. Conclusions. H 2 CO is only desorbed from interstellar ices via a dominant sub-monolayer desorption process (E = 27.1 +/− 0.5 kJ mol −1 ). The H 2 CO which has not desorbed during this sub-monolayer desorption polymerises upon reaction with H 2 O, and does not desorb as H 2 CO at higher temperature.

show abstract

Interaction of D2 with H2O amorphous ice studied by temperature-programed desorption experiments

Cited by 91 publications

References 58 publications

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

CO₂formation on interstellar dust grains: a detailed study of the barrier of the CO + O channel

The desorption of H₂CO from interstellar grains analogues

Contact Info

Product

Resources

About

Interaction of D2 with H2O amorphous ice studied by temperature-programed desorption experiments

Cited by 91 publications

References 58 publications

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

Changes in the morphology of interstellar ice analogues after hydrogen atom exposure

CO2formation on interstellar dust grains: a detailed study of the barrier of the CO + O channel

The desorption of H2CO from interstellar grains analogues

Contact Info

Product

Resources

About

CO₂formation on interstellar dust grains: a detailed study of the barrier of the CO + O channel

The desorption of H₂CO from interstellar grains analogues