CO$\mathsf{_{2}}$ synthesis in solid CO by Lyman-<i>α</i> photons   and 200 keV protons

Loeffler, M. J.; Baratta, G. A.; Palumbo, M. E.; Strazzulla, G.; Baragiola, R. A.

doi:10.1051/0004-6361:20042256

Cited by 139 publications

(166 citation statements)

References 39 publications

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“…This feature includes the bands of several C n O 2 species;see Table 2. The features between 2100 and2040 cm −1 also survive up to 210 K. The feature around The features listed in Table 2 testify that after X-ray irradiation of a CO ice we obtain all the products of the ultraviolet irradiation using the hydrogen lamp (Gerakines et al 1996;Loeffler et al 2005) A refractory residue is left after the CO ice is fully desorbed;see Figure 7. Three main peaks are detected at 3303, 2155, and 1785 cm −1 , and a fourth at 1762 cm −1 blended with the 1785 cm −1 band.…”

Section: Products Of the Irradiationmentioning

confidence: 74%

“…Such results havebeen questioned by Loeffler et al (2005), who studied the formation of carbon dioxide from solid CO at 16K induced by Lyα photolysis (using a microwave-discharge hydrogen lamp) and irradiation with 200 keV protons. These authors determined that while the initial production rate of CO 2 per unit energy deposited is similar for both sources, the equilibrium concentration is three times higher in the case of ion irradiation.…”

Section: Comparison With Other Experimentsmentioning

confidence: 99%

“…These authors determined that while the initial production rate of CO 2 per unit energy deposited is similar for both sources, the equilibrium concentration is three times higher in the case of ion irradiation. To compare our outcomes with the Loeffler et al (2005) results, we characterize the CO 2 column densities produced at the end of our experiments with the energy absorbed per 16 amu molecule. In the X-ray experiments the CO 2 column densities result inN 5.2 10 CO 16…”

Section: Comparison With Other Experimentsmentioning

confidence: 99%

“…Laboratory studies of the evolution of interstellar ice analogs under the effect of photon irradiation and ionized particles have greatly contributed to our understanding of the chemistry of complex organic molecules synthesized in space. In particular, the chemical modifications of CO ices, both pure or in mixture, have been studied under the effect of vacuum (Gerakines et al 1996;Gerakines & Moore 2001;Cottin et al 2003;Loeffler et al 2005;Chen et al 2014) and extreme-ultraviolet radiation (Wu et al 2005), ions (Gerakines & Moore 2001;Trottier & Brooks 2004;Loeffler et al 2005;Domaracka et al 2010) and electrons (Jamieson et al 2006). Muñoz Caro et al (2010) measured the photodesorption yield of CO ice under ultraviolet irradiation, finding the release yield at 15 K to be about one order of magnitude higher than previous estimates.…”

Section: Introductionmentioning

confidence: 99%

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Chemical Evolution of a Co Ice Induced by Soft X-Rays

Ciaravella

Chen

Cecchi‐Pestellini

et al. 2016

ApJ

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We irradiated a pure carbon monoxide ice with soft X-rays of energies up to 1.2 keV. The experiments were performed using the spherical grating monochromator beamline at the National Synchrotron Radiation Research Center in Taiwan, exploiting both monochromatic (at 0.3 and 0.55 keV) and broader energy (0.25-1.2 keV) fluxes. The infrared spectra of the irradiated ices showed the formation of a number of products such as polycarbon monoand dioxides C n O m , and chains containing up to 10 carbon atoms. While a gentle increase in the energy absorbed by the ice sample is reflected by an increase in the column densities of newly born species, such correlation breaks down at very high fluxes. In this regime the production yield falls down sharply by about a factor of 100. The refractory residue obtained in the broad energy irradiation is a "compromise" between those obtained with proton irradiation of C 3 O 2 and CO ices in previous experiments. Finally, we discuss the possible implications for space chemistry

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Section: Products Of the Irradiationmentioning

confidence: 74%

Section: Comparison With Other Experimentsmentioning

confidence: 99%

Section: Comparison With Other Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Ciaravella

Chen

Cecchi‐Pestellini

et al. 2016

ApJ

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“…UV radiation can produce CO 2 from CO and H 2 O ices through photochemistry, photodesorb pure CO 2 ice, and photodissociate CO 2 into CO and thus transform the pure CO 2 ice into a CO 2 :CO mixture (Watanabe & Kouchi 2002;Loeffler et al 2005;Öberg et al 2009;Gerakines et al 1996). Of these processes, CO 2 formation through photochemistry should not affect the amount of pure CO 2 ice, since CO 2 then forms mixed with H 2 O and CO ices.…”

Section: Astrophysical Implicationsmentioning

confidence: 99%

Quantification of segregation dynamics in ice mixtures

Öberg¹,

Fayolle²,

Cuppen

et al. 2009

A&A

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Context. The observed presence of pure CO 2 ice in protostellar envelopes, revealed by a double peaked 15 μm band, is often attributed to thermally induced ice segregation. The temperature required for segregation is however unknown because of lack of quantitative experimental data and this has prevented the use of ice segregation as a temperature probe. In addition, quantitative segregation studies are needed to characterize diffusion in ices, which underpins all ice dynamics and ice chemistry. Aims. This study aims to quantify the segregation mechanism and barriers in different H 2 O:CO 2 and H 2 O:CO ice mixtures. Methods. The investigated ice mixtures cover a range of astrophysically relevant ice thicknesses and mixture ratios. The ices are deposited at 16-50 K under (ultra-)high vacuum conditions. Segregation is then monitored, at 40-70 K in the CO 2 mixtures and at 23-27 K in the CO mixtures, through infrared spectroscopy. The CO 2 and CO band shapes are distinctly different in pure and mixed ices and can thus be used to measure the fraction of segregated ice as a function of time. The segregation barrier is determined using rate equations and the segregation mechanism is investigated through Monte Carlo simulations. Results. Thin (8-37 ML) H 2 O ice mixtures, containing either CO 2 or CO, segregate sequentially through surface processes, followed by an order of magnitude slower bulk diffusion. Thicker ices (>100 ML) segregate through a bulk process, which is faster than even surface segregation in thin ices. The thick ices must therefore be either more porous or segregate through a different mechanism, e.g. a phase transition, compared to the thin ices. The segregation dynamics of thin ices are reproduced qualitatively in Monte Carlo simulations of surface hopping and pair swapping. The experimentally determined surface-segregation rates follow the Ahrrenius law with a barrier of 1080 ± 190 K for H 2 O:CO 2 ice mixtures and 300 ± 100 K for H 2 O:CO mixtures. Though the barrier is constant with ice mixing ratio, the segregation rate increases with CO 2 concentration. Conclusions. Dynamical ice processes can be quantified through a combination of experiments and different model techniques and they are not scale independent as previously assumed. The derived segregation barrier for thin H 2 O:CO 2 ice mixtures is used to estimate the surface segregation temperature during low-mass star formation to be 30 ± 5 K. Both surface and bulk segregation is proposed to be a general feature of ice mixtures when the average bond strengths of the mixture constituents in pure ice exceeds the average bond strength in the ice mixture.

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Cosmic ion induced chemistry in ices

Strazzulla

Garozzo

Fulvio

et al. 2011

Rend. Fis. Acc. Lincei

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Since many years, the Laboratory for Experimental Astrophysics in Catania (Italy) has given a contribution to a number of experiments with the aim to investigate the physico-chemical effects induced by fast ions irradiating astrophysical relevant materials. Here, we review some of the most recent results, namely irradiation of mixtures of solid CO and S-bearing molecules. In the interstellar medium, two or more icy compounds can coexist to form ice mantles on grains in two different forms: either they can be mixed together or form separated layers (ice segregation). Thus experiments have been performed with targets prepared at low T (15-20 K) both by a co-deposition of a mixture of two gas compounds (CO and SO 2 or H 2 S) and with targets prepared by deposition of CO ices on a previously deposited SO 2 or H 2 S layer. Samples have been irradiated with 200 keV protons with the aim of simulating a cosmic ion bombardment of interstellar ices. The results show that new chemical species are formed; in particular, OCS and CS 2 . The astrophysical relevance of the results is discussed.

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CO$\mathsf{_{2}}$ synthesis in solid CO by Lyman-α photons and 200 keV protons

Cited by 139 publications

References 39 publications

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Quantification of segregation dynamics in ice mixtures

Cosmic ion induced chemistry in ices

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