New measurements on water ice photodesorption and product formation under ultraviolet irradiation

Abstract

The photodesorption of icy grain mantles has been claimed to be responsible for the abundance of gas-phase molecules toward cold regions. Being water a ubiquitous molecule, it is crucial to understand its role in photochemistry and its behavior under an ultraviolet field. We report new measurements on the UV-photodesorption of water ice and its H${}_2$, OH, and O${}_2$ photoproducts using a calibrated quadrupole mass spectrometer. Solid water was deposited under ultra-high-vacuum conditions and then UV-irradiated at various temperatures starting from 8 K with a microwave discharged hydrogen lamp. Deuterated water was used for confirmation of the results. We found a photodesorption yield of 1.3 $\times$ 10${}^{-3}$ molecules per incident photon for water, and 0.7 $\times$ 10${}^{-3}$ molecules per incident photon for deuterated water at the lowest irradiation temperature, 8 K. The photodesorption yield per absorbed photon is given and comparison with astrophysical scenarios, where water ice photodesorption could account for the presence of gas-phase water toward cold regions in the absence of a thermal desorption process is addressed.

11 pages, 12 figures, 3 tables

References in corpus (4)

• Imaging the water-snow line during a protostellar outburst
• Thermal desorption of circumstellar and cometary ice analogs
• Vacuum-UV spectroscopy of interstellar ice analogs. I. Absorption cross-sections of polar-ice molecules
• Herschel -PACS observations of [OI] and H2O in Cha II

Cited by in corpus (6)

• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• Photodesorption of water ice from dust grains and thermal desorption of cometary ices studied by the INSIDE experiment
• Cosmic ray sputtering yield of interstellar ice mantles: CO and CO2 ice thickness dependence
• Direct Determination of the Activation Energy for Diffusion of OH Radicals on Water Ice
• Mechanism of Indirect Photon-induced Desorption at the Water Ice Surface
• ${}^{13}$CO and ${}^{13}$CO${}_2$ ice mixtures with N${}_2$ in photon energy transfer studies