Water is the main constituent of interstellar ices, and it plays a key role in the evolution of many regions of the interstellar medium, from molecular clouds to planet-forming disks1. In cold regions of the interstellar medium, water is expected to be completely frozen out onto the dust grains. Nonetheless, observations indicate the presence of cold water vapour, implying that non-thermal desorption mechanisms are at play. Photodesorption by ultraviolet photons has been proposed to explain these observations2,3, with the support of extensive experimental and theoretical work on ice analogues4,5,6. In contrast, photodesorption by X-rays, another viable mechanism, has been little studied. The potential of this process to desorb key molecules such as water, intact rather than fragmented or ionized, remains unexplored. We experimentally investigated X-ray photodesorption from water ice, monitoring all desorbing species. We found that desorption of neutral water is efficient, while ion desorption is minor. We derived yields that can be implemented in astrochemical models. These results open up the possibility of taking into account the X-ray photodesorption process in the modelling of protoplanetary disks or X-ray-dominated regions.
This is a preview of subscription content, access via your institution
Subscribe to Nature+
Get immediate online access to the entire Nature family of 50+ journals
Subscribe to Journal
Get full journal access for 1 year
only $9.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
van Dishoeck, E. F., Bergin, E. A., Lis, D. C. & Lunine, J. I. in Protostars and Planets VI (eds Beuther, H. et al.) 835–858 (Univ. Arizona Press, Tucson, 2014).
Hogerheijde, M. R. et al. Detection of the water reservoir in a forming planetary system. Science 334, 338–340 (2011).
Caselli, P. et al. First detection of water vapor in a pre-stellar core. Astrophys. J. Lett. 759, L37 (2012).
Arasa, C., Koning, J., Kroes, G.-J., Walsh, C. & van Dishoeck, E. F. Photodesorption of H2O, HDO, and D2O ice and its impact on fractionation. Astron. Astrophys. 575, A121 (2015).
Muñoz Caro, G. M. et al. Photodesorption and physical properties of CO ice as a function of temperature. Astron. Astrophys. 589, A19 (2016).
Bertin, M. et al. UV photodesorption of methanol in pure and CO-rich ices: desorption rates of the intact molecules and the photofragments. Astrophys. J. Lett. 817, L12 (2016).
Aikawa, Y. & Herbst, E. Molecular evolution in protoplanetary disks. Two-dimensional distributions and column densities of gaseous molecules. Astron. Astrophys. 351, 233–246 (1999).
Walsh, C., Nomura, H., Millar, T. J. & Aikawa, Y. Chemical processes in protoplanetary disks. II. On the importance of photochemistry and X-ray ionization. Astrophys. J. 747, 114 (2012).
Maloney, P. R., Hollenbach, D. J. & Tielens, A. G. G. M. X-ray-irradiated molecular gas. I. Physical processes and general results. Astrophys. J. 466, 561–584 (1996).
Meijerink, R., Spaans, M. & Israel, F. P. Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models. Astron. Astrophys. 461, 793–811 (2007).
Walsh, C., Millar, T. J. & Nomura, H. Chemical processes in protoplanetary disks. Astrophys. J. 722, 1607–1623 (2010).
Stäuber, P., Jørgensen, J. K., van Dishoeck, E. F., Doty, S. D. & Benz, A. O. Water destruction by X-rays in young stellar objects. Astron. Astrophys. 453, 555–565 (2006).
Cleeves, L. I., Bergin, E. A., Qi, C., Adams, F. C. & Öberg, K. I. Constraining the X-ray and cosmic-ray ionization chemistry of the TW Hya protoplanetary disk: evidence for a sub-interstellar cosmic-ray rate. Astrophys. J. 799, 204 (2015).
Rosenberg, R. A.et al. K-shell excitation of D2O and H2O ice: photoion and photoelectron yields. Phys. Rev. B 28, 3026–3030 1983).
Coulman, D. et al. Excitation, deexcitation, and fragmentation in the core region of condensed and adsorbed water. J. Chem. Phys. 93, 58–75 (1990).
Mase, K., Nagasono, M., Tanaka, S.-i, Sekitani, T. & Nagaoka, S.-i Ion desorption from molecules condensed at low temperature: a study with electron-ion coincidence spectroscopy combined with synchrotron radiation (review). Low Temp. Phys. 29, 243–258 (2003).
Pilling, S. & Andrade, D. P. P. in X-Ray Spectroscopy (ed. Sharma, S. K.) Ch. 10 (InTech, London, 2012); https://doi.org/10.5772/29591
Nilsson, A. et al. X-ray absorption spectroscopy and X-ray Raman scattering of water and ice; an experimental view. J. Electron Spectrosc. 177, 99–129 (2010).
Parent, P., Laffon, C., Mangeney, C., Bournel, F. & Tronc, M. Structure of the water ice surface studied by X-ray absorption spectroscopy at the O K-edge. J. Chem. Phys. 117, 10842–10851 (2002).
Laffon, C., Lacombe, S., Bournel, F. & Parent, P. Radiation effects in water ice: a near-edge X-ray absorption fine structure study. J. Chem. Phys. 125, 204714 (2006).
Petrik, N. G. & Kimmel, G. A. Electron-stimulated sputtering of thin amorphous solid water films on Pt(111). J. Chem. Phys. 123, 054702 (2005).
Yabushita, A., Hama, T. & Kawasaki, M. Photochemical reaction processes during vacuum-ultraviolet irradiation of water ice. J. Photoch. Photobio. C 16, 46–61 (2013).
Cruz-Diaz, G. A., Martn-Doménech, R., Moreno, E., Muñoz Caro, G. M. & Chen, Y.-J. New measurements on water ice photodesorption and product formation under ultraviolet irradiation. Mon. Not. R. Astron. Soc. 474, 3080–3089 (2018).
Arasa, C., Andersson, S., Cuppen, H. M., van Dishoeck, E. F. & Kroes, G.-J. Molecular dynamics simulations of the ice temperature dependence of water ice photodesorption. J. Chem. Phys. 132, 184510 (2010).
Nomura, H., Aikawa, Y., Tsujimoto, M., Nakagawa, Y. & Millar, T. J. Molecular hydrogen emission from protoplanetary disks. II. Effects of X-ray irradiation and dust evolution. Astrophys. J. 661, 334–353 (2007).
Braito, V. et al. The XMM-Newton and BeppoSAX view of the ultra luminous infrared galaxy MKN 231. Astron. Astrophys. 420, 79–88 (2004).
Cecchi-Pestellini, C. & Aiello, S. Cosmic ray induced photons in dense interstellar clouds. Mon. Not. R. Astron. Soc. 258, 125–133 (1992).
Dartois, E. et al. Heavy ion irradiation of crystalline water ice: cosmic ray amorphisation cross-section and sputtering yield. Astron. Astrophys. 576, A125 (2015).
Walsh, C., Nomura, H. & van Dishoeck, E. The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime. Astron. Astrophys. 582, A88 (2015).
Sacchi, M. et al. The SEXTANTS beamline at SOLEIL: a new facility for elastic, inelastic and coherent scattering of soft X-rays. J. Phys. Conf. Ser. 425, 072018 (2013).
Doronin, M., Bertin, M., Michaut, X., Philippe, L. & Fillion, J.-H. Adsorption energies and prefactor determination for CH3OH adsorption on graphite. J. Chem. Phys. 143, 084703 (2015).
Naumkin, A. V., Kraut-Vass, A., Gaarenstroom, S. W. & Powell, C. J. NIST X-ray Photoelectron Spectroscopy Database (National Institute of Standards and Technology, 2012); https://srdata.nist.gov/xps/
Dupuy, R. et al. Spectrally-resolved UV photodesorption of CH4 in pure and layered ices. Astron. Astrophys. 603, A61 (2017).
Orient, O. J. & Strivastava, S. K. Electron impact ionisation of H2O, CO, CO2 and CH4. J. Phys. B 20, 3923–3936 (1987).
Straub, H. C., Renault, P., Lindsay, B. G., Smith, K. A. & Stebbings, R. F. Absolute partial cross sections for electron-impact ionization of H2, N2, and O2 from threshold to 1000 eV. Phys. Rev. A 54, 2146–2153 (1996).
Vegard, I. Struktur und Leuchtfähigkeit von festem Kohlenoxyd. Z. Phys. A Hadron Nucl. 61, 185–190 (1930).
Fayolle, E. C. et al. CO ice photodesorption: a wavelength-dependent study. Astrophys. J. Lett. 739, L36 (2011).
Cruz-Diaz, G. A., Muñoz Caro, G. M., Chen, Y.-J. & Yih, T.-S. Vacuum-UV spectroscopy of interstellar ice analogs. I. Absorption cross-sections of polar-ice molecules. Astron. Astrophys. 562, A119 (2014).
Berkowitz, J. Atomic and Molecular Photoabsorption: Absolute Total Cross Sections (Academic, London, 2002).
Bertin, M. et al. UV photodesorption of interstellar CO ice analogues: from subsurface excitation to surface desorption. Phys. Chem. Chem. Phys. 14, 9929–9935 (2012).
Tîmneanu, N., Caleman, C., Hajdu, J. & van der Spoel, D. Auger electron cascades in water and ice. Chem. Phys. 299, 277–283 (2004).
Andersson, S. & van Dishoeck, E. F. Photodesorption of water ice. Astron. Astrophys. 491, 907–916 (2008).
DeSimone, A. J., Crowell, V. D., Sherrill, C. D. & Orlando, T. M. Mechanisms of H2O desorption from amorphous solid water by 157-nm irradiation: an experimental and theoretical study. J. Chem. Phys. 139, 164702 (2013).
Kimmel, G. A., Orlando, T. M., Vézina, C. & Sanche, L. Low-energy electron-stimulated production of molecular hydrogen from amorphous water ice. J. Chem. Phys. 101, 3282–3286 (1994).
Redlich, B., Zacharias, H., Meijer, G. & von Helden, G. Resonant infrared laser-induced desorption of methane condensed on NaCl(100): isotope mixture experiments. J. Chem. Phys. 124, 044704 (2006).
Hovington, P., Drouin, D. & Gauvin, R. CASINO: a new Monte Carlo code in C language for electron beam interaction—part I: description of the program. Scanning 19, 1–14 (2006).
Bethell, T. J. & Bergin, E. A. Photoelectric cross-sections of gas and dust in protoplanetary disks. Astrophys. J. 740, 7 (2011).
Dupuy, R. et al. The efficient photodesorption of nitric oxide (NO) ices: a laboratory astrophysics study. Astron. Astrophys. 606, L9 (2017).
Rab, C. et al. X-ray radiative transfer in protoplanetary disks: the role of dust and X-ray background fields. Astron. Astrophys. 609, A91 (2018).
We thank C. Walsh for insights on X-rays in protoplanetary disks, D. Lis for comments on the paper and P. Marie-Jeanne for technical support. We acknowledge SOLEIL for the provision of synchrotron radiation facilities under project 20161406, and we thank N. Jaouen and the SEXTANTS team for their help on the beamline. This work was supported by the Programme National ‘Physique et Chimie du Milieu Interstellaire’ (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES. Financial support from LabEx MiChem, part of the French state funds managed by the ANR within the investissements d’avenir programme under reference ANR-11-10EX-0004-02, and by the Ile-de-France region DIM ACAV programme, is gratefully acknowledged. This work was done in collaboration with and through financial support from the European Organization for Nuclear Research (CERN) under collaboration agreement KE3324/TE.
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Dupuy, R., Bertin, M., Féraud, G. et al. X-ray photodesorption from water ice in protoplanetary disks and X-ray-dominated regions. Nat Astron 2, 796–801 (2018). https://doi.org/10.1038/s41550-018-0532-y