Thermal desorption of circumstellar and cometary ice analogs

Martín-Doménech, R.; Muñoz, G. M.; Bueno, J.; Goesmann, Fred

doi:10.1051/0004-6361/201322824

Cited by 110 publications

(106 citation statements)

References 44 publications

(80 reference statements)

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“…This TPD behavior is similar to what was previously reported for CO ices accreted at a fixed temperature under different conditions (see, e.g., Collings et al 2004;Martín-Doménech et at. 2014).…”

Section: Resultssupporting

confidence: 90%

“…However, once the temperature decreases below 26.5 K, the solid CO IR feature is observed, increasing its intensity at a constant rate (see Figure 3, right panel), which corresponds to an accretion rate of 1.5 ML minute −1 . This feature does not present any shoulder at ∼2152 cm −1 , which is typical of CO molecules interacting with dangling OH bonds (see, e.g., Collings et al 2003a;Martín-Doménech et at. 2014).…”

Section: Experimental Setup: the Interstellar Astrochemistry Chambermentioning

confidence: 99%

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CO Depletion: A Microscopic Perspective

Cazaux

Martín-Doménech

Chen

et al. 2017

ApJ

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In regions where stars form, variations in density and temperature can cause gas to freeze out onto dust grains forming ice mantles, which influences the chemical composition of a cloud. The aim of this paper is to understand in detail the depletion (and desorption) of CO on (from) interstellar dust grains. Experimental simulations were performed under two different (astrophysically relevant) conditions. In parallel, Kinetic Monte Carlo simulations were used to mimic the experimental conditions. In our experiments, CO molecules accrete onto water ice at temperatures below 27 K, with a deposition rate that does not depend on the substrate temperature. During the warm-up phase, the desorption processes do exhibit subtle differences, indicating the presence of weakly bound CO molecules, therefore highlighting a low diffusion efficiency. IR measurements following the ice thickness during the TPD confirm that diffusion occurs at temperatures close to the desorption. Applied to astrophysical conditions, in a pre-stellar core, the binding energies of CO molecules, ranging between 300 and 850 K, depend on the conditions at which CO has been deposited. Because of this wide range of binding energies, the depletion of CO as a function of A V is much less important than initially thought. The weakly bound molecules, easily released into the gas phase through evaporation, change the balance between accretion and desorption, which result in a larger abundance of CO at high extinctions. In addition, weakly bound CO molecules are also more mobile, and this could increase the reactivity within interstellar ices.

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Section: Resultssupporting

confidence: 90%

Section: Experimental Setup: the Interstellar Astrochemistry Chambermentioning

confidence: 99%

CO Depletion: A Microscopic Perspective

Cazaux

Martín-Doménech

Chen

et al. 2017

ApJ

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“…The presence of these photoproducts in the ice leads to the loss of the double-peak structure of the degenerate bending modes of CO 2 (see right panel of Fig. 1), as has previously been reported for carbon dioxide in multicomponent ice analogs (Sandford & Allamandola 1990;Martín-Doménech et al 2014). Similarly, the shoulder of the C=O stretching band of CO 2 peaking at ∼2328 cm −1 Fig.…”

Section: Ir Spectra Of Co 2 Ice During Irradiationsupporting

confidence: 73%

UV photoprocessing of CO₂ice: a complete quantification of photochemistry and photon-induced desorption processes

Martín-Doménech

Manzano-Santamaría

Muñoz

et al. 2015

A&A

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Context. Ice mantles that formed on top of dust grains are photoprocessed by the secondary ultraviolet (UV) field in cold and dense molecular clouds. UV photons induce photochemistry and desorption of ice molecules. Experimental simulations dedicated to ice analogs under astrophysically relevant conditions are needed to understand these processes. Aims. We present UV-irradiation experiments of a pure CO 2 ice analog. Calibration of the quadrupole mass spectrometer allowed us to quantify the photodesorption of molecules to the gas phase. This information was added to the data provided by the Fourier transform infrared spectrometer on the solid phase to obtain a complete quantitative study of the UV photoprocessing of an ice analog. Methods. Experimental simulations were performed in an ultra-high vacuum chamber. Ice samples were deposited onto an infrared transparent window at 8K and were subsequently irradiated with a microwave-discharged hydrogen flow lamp. After irradiation, ice samples were warmed up until complete sublimation was attained. Results. Photolysis of CO 2 molecules initiates a network of photon-induced chemical reactions leading to the formation of CO, CO 3 , O 2 , and O 3 . During irradiation, photon-induced desorption of CO and, to a lesser extent, O 2 and CO 2 took place through a process called indirect desorption induced by electronic transitions, with maximum photodesorption yields (Y pd ) of ∼1.2 × 10 −2 molecules incident photon −1 , ∼9.3 × 10 −4 molecules incident photon −1 , and ∼1.1 × 10 −4 molecules incident photon −1 , respectively. Conclusions. Calibration of mass spectrometers allows a direct quantification of photodesorption yields instead of the indirect values that were obtained from infrared spectra in most previous works. Supplementary information provided by infrared spectroscopy leads to a complete quantification, and therefore a better understanding, of the processes taking place in UV-irradiated ice mantles.

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“…We note that experiments show that the evaporation of icy mixtures occurs sequentially, i.e., through diffusion from subsurface ice layers (Martín-Doménech et al 2014), although partial entrapment is possible (Fayolle et al 2011). This supports our model with mobile bulk-ice molecules.…”

Section: Chemical Modelsupporting

confidence: 85%

Chemical fractionation of deuterium in the protosolar nebula

Kalvāns

Shmeld

Kalnin

et al. 2017

Mon. Not. R. Astron. Soc.

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Understanding gas-grain chemistry of deuterium in star-forming objects may help to explain their history and present state. We aim to clarify how processes in ices affect the deuterium fractionation. In this regard, we investigate a Solar-mass protostellar envelope using an astrochemical rate-equation model that considers bulk-ice chemistry. The results show a general agreement with the molecular D/H abundance ratios observed in low-mass protostars. The simultaneous processes of ice accumulation and rapid synthesis of HD on grain surfaces in the prestellar core hampers the deuteration of icy species. The observed very high D/H ratios exceeding 10 per cent, i.e., superdeuteration, are reproduced for formaldehyde and dimethyl ether, but not for other species in the protostellar envelope phase. Chemical transformations in bulk ice lower D/H ratios of icy species and do not help explaining the super-deuteration. In the protostellar phase, the D 2 O/HDO abundance ratio was calculated to be higher than the HDO/H 2 O ratio owing to gas-phase chemistry. Species that undergo evaporation from ices have high molecular D/H ratio and a high gas-phase abundance.

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Thermal desorption of circumstellar and cometary ice analogs

Cited by 110 publications

References 44 publications

CO Depletion: A Microscopic Perspective

CO Depletion: A Microscopic Perspective

UV photoprocessing of CO₂ice: a complete quantification of photochemistry and photon-induced desorption processes

Chemical fractionation of deuterium in the protosolar nebula

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Thermal desorption of circumstellar and cometary ice analogs

Cited by 110 publications

References 44 publications

CO Depletion: A Microscopic Perspective

CO Depletion: A Microscopic Perspective

UV photoprocessing of CO2ice: a complete quantification of photochemistry and photon-induced desorption processes

Chemical fractionation of deuterium in the protosolar nebula

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UV photoprocessing of CO₂ice: a complete quantification of photochemistry and photon-induced desorption processes