UV photoprocessing of CO<sub>2</sub>ice: a complete quantification of photochemistry and photon-induced desorption processes

Martín-Doménech, R.; Manzano-Santamaría, J.; Muñoz, G. M.; Cruz-Díaz, G. A.; Chen, Yu-Jung; Herrero, Vı́ctor J.; Tanarro, Isabel

doi:10.1051/0004-6361/201526003

Cited by 66 publications

(94 citation statements)

References 65 publications

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“…The CO photodesorption rate furthermore strongly depends on the deposition temperature, as has been discussed by several groups (Öberg et al 2009b;Muñoz Caro et al 2010, 2016. In parallel, many more studies have been performed on other pure ices, including H 2 O, N 2 , CO 2 , O 2 (O 3 ), and CH 3 OH, as well as a few mixed ices, CO:N 2 , CO:H 2 O, and CO:CH 3 OH (Öberg et al 2009a;Hama et al 2010;Chen et al 2011;Bahr & Baragiola 2012;Bertin et al 2012Bertin et al , 2013Bertin et al , 2016Fayolle et al 2013;Yuan & Yates 2013;Fillion et al 2014;Zhen & Linnartz 2014;Martín-Doménech et al 2015). In many of these studies it became clear that upon VUV photolysis, molecules not only photodesorb, but may also be involved in photo-induced reactions (Öberg 2016) substantially complicating the analysis, as photoproducts may photodesorb as well (see e.g.…”

Section: Introductionmentioning

confidence: 86%

A novel approach to measure photodesorption rates of interstellar ice analogues

Paardekooper

Fedoseev

Riedo

et al. 2016

A&A

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Context. In recent years photodesorption rates have been determined in dedicated laboratory experiments for a number of different interstellar ice analogues. These rates are important in order to model non-thermal desorption processes that, for example, affect gas-phase abundances of species and determine the position of photo-induced snow lines in protoplanetary disks. However, different groups using similar experiments have found significant deviating photodesorption values. Aims. Here a new measurement concept is introduced that allows photodesorption rates to be determined following a different experimental approach. The potential of this method is demonstrated using the example of pure CO ice, the solid that gives the most striking discrepancies in the published results. Methods. The new experimental approach uses laser desorption post-ionisation time-of-flight mass spectrometry. It is based on the concept that the physical and geometrical properties of the plume obtained by laser induced desorption of the ice directly depend on the original ice thickness. This allows the ice loss to be determined as function of vacuum ultraviolet (VUV) fluence, which results in a photodesorption rate. The method has the additional advantage that it records all ice species, including photoproducts generated by the VUV irradiation. As a consequence, the method introduced here is also suited to determine the overall photodesorption rate of mixed ices. Results. The photodesorption rate for CO ice at 20 K has been determined as (1.4 ± 0.7) × 10 −3 molecules per incident VUV photon. This result is compared to existing experimental and theoretical values and the astronomical relevance is discussed.

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Section: Introductionmentioning

confidence: 86%

A novel approach to measure photodesorption rates of interstellar ice analogues

Paardekooper

Fedoseev

Riedo

et al. 2016

A&A

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“…This value is on the order of the observed H2O photodesorption during photoprocessing of pure H2O ices using the same UV lamp, (Cruz-Díaz et al (2017)), while it is one order of magnitude lower than the photodesorption yield of CO molecules during photoprocessing of a pure CO ice (Muñoz Caro et al (2010)), and one order of magnitude higher than that measured for CO2 (see Table 4) under similar conditions (Martín-Doménech et al (2015)). Photodesorption of NH3 molecules from an ice mixture dominated by water will be addressed in a forthcoming paper, and is expected to be lower than the value presented in this paper for segregated (pure) NH3 ice (Loeffler & Baragiola (2010)).…”

Section: Astrophysical Implicationsmentioning

confidence: 61%

“…A brief description of the experimental setup and the protocol followed during the experimental simulations is provided below (see Muñoz Caro et al (2010);Martín-Doménech et al (2015); Cruz-Díaz et al (2016);Martín-Doménech et al (2016) for more details). Pure amorphous ammonia ice samples were deposited from the gas phase onto a KBr window at 8 K used as the substrate, upon introduction of NH3 (gas, Praxair 99.999%) into the chamber.…”

Section: Methodsmentioning

confidence: 99%

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UV photoprocessing of NH3 ice: photon-induced desorption mechanisms

Martín-Doménech

Cruz-Díaz

Muñoz

2017

Monthly Notices of the Royal Astronomical Society

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Ice mantles detected on the surface of dust grains toward the coldest regions of the interstellar medium can be photoprocessed by the secondary ultraviolet (UV) field present in dense cloud interiors. In this work, we present UV-irradiation experiments under astrophysically relevant conditions of pure NH 3 ice samples in an ultra-high vacuum chamber where solid samples were deposited onto a substrate at 8 K. The ice analogs were subsequently photoprocessed with a microwave-discharged hydrogen-flow lamp. The induced radiation and photochemistry led to the production of H 2 , N 2 and N 2 H 4 . In addition, photodesorption to the gas phase of the original ice component, NH 3 , and two of the three detected photoproducts, H 2 and N 2 , was observed thanks to a quadrupole mass spectrometer (QMS). Calibration of the QMS allowed quantification of the photodesorption yields, leading to Y pd (NH 3 ) = 2.1 +2.1 −1.0 x 10 −3 molecules incident photon , which remained constant during the whole experiments, while photodesorption of H 2 and N 2 increased with fluence, pointing toward an indirect photodesorption mechanism involving energy transfer for these species. Photodesorption yield of N 2 molecules after a fluence equivalent to that experienced by ice mantles in space was similar to that of the NH 3 molecules (Y pd (N 2 ) = 1.7 +1.7 −0.9 x 10 −3 molecules incident photon ).

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“…The presence of H 2 O or other molecules in the ice, like N 2 , has an impact on the photodesorption yield of CO (Bertin et al 2012(Bertin et al , 2013. In pure CO 2 ice irradiation experiments, where CO is a photoproduct, a UV fluence, which is similar to that experienced by ice mantles during the quiescent molecular cloud lifetime, only led to ∼4% photodesorption of the CO molecules formed (Martín-Doménech et al 2015). Photodesorption rate values per incident photon, as reported by Fayolle et al (2011) for different photon energies, were converted to rates in molecules that desorb per absorbed photon in the ice, leading to values near unity or higher (Cruz-Diaz et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Photodesorption and physical properties of CO ice as a function of temperature

Muñoz

Chen

Aparicio

et al. 2016

A&A

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Context. Ice photodesorption has been the topic of recent studies that aim to interpret the abundances of gas-phase molecules, in particular CO, toward cold interstellar regions. But little is known about the effect of the ice's physical properties on the photodesorption rate. The linear decrease observed in the photodesorption rate, as a function of increasing CO ice deposition temperature, was provisionally attributed to a more compact CO ice structure. Aims. The goal of this work is to monitor the physical properties of solid CO as a function of ice deposition temperature. Then, we evaluate the possible link between the structure of ice and the ice's photodesorption rate. Methods. Infrared spectroscopy is an efficient tool to monitor the structural evolution of pure ices during warm-up or irradiation. The infrared absorption bands of molecular ice components observed toward various space environments allow for the detection of H 2 O, CO, CO 2 , CH 3 OH, NH 3 , etc. Typically, a pure ice that is composed of one of these species displays significant changes in their mid-infrared band profiles as a result of warm-up. But, at most, only very subtle changes appear in the narrow CO ice infrared absorption band as the result of warm-up. We, therefore, also used vacuum-ultraviolet spectroscopy of CO ice to monitor the effect of temperature in the physical properties of the ice. Finally, temperature-programmed desorption and photo-desorption experiments for different CO ice deposition temperatures were performed. Results. Mid-infrared and vacuum-ultraviolet spectroscopy showed that warm-up of CO ice that is deposited at 8 K did not lead to structural changes. Only CO ice samples deposited at temperatures above 20 K displayed different spectroscopic properties compared to lower deposition temperatures. The observed gradual and linear drop in the photodesorption rate of CO ice, as a function of increasing ice deposition temperature in the 7 to 20 K range, is, therefore, not due to a gradual re-structuring toward a more compact and crystalline ice, which is only triggered above 20 K and increases for higher deposition temperatures. Conclusions. We suggest that this decrease of the photodesorption rate is related to the disorder of CO dipole molecules within the amorphous or glassy state, which influences the necessary transfer of photon energy from the first excited molecule to the desorbing molecule on the ice surface. The photodesorption yield of CO deposited at 20 K is about four times lower than at 7 K. Dust models should adopt CO photodesorption yields that are compatible with the thermal history of the cloud.

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

Cited by 66 publications

References 65 publications

A novel approach to measure photodesorption rates of interstellar ice analogues

A novel approach to measure photodesorption rates of interstellar ice analogues

UV photoprocessing of NH3 ice: photon-induced desorption mechanisms

Photodesorption and physical properties of CO ice as a function of temperature

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

Cited by 66 publications

References 65 publications

A novel approach to measure photodesorption rates of interstellar ice analogues

A novel approach to measure photodesorption rates of interstellar ice analogues

UV photoprocessing of NH3 ice: photon-induced desorption mechanisms

Photodesorption and physical properties of CO ice as a function of temperature

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