2016/03/07 by Jiao He, Kinsuk Acharyya, Gianfranco Vidali · 1 citation
Physics and Astronomy · #astro-ph.IM
paper · pdf · doi:10.3847/0004-637x/825/2/89
10 pages, 14 figures, submitted to ApJ
arxiv created 2016/03/07 · arxiv updated 2016/07/13
We measured the binding energy of N2, CO, O2, CH4, and CO2 on non-porous (compact) amorphous solid water (np-ASW), of N2 and CO on porous amorphous solid water (p-ASW), and of NH3 on crystalline water ice. We were able to measure binding energies down to a fraction of 1% of a layer, thus making these measurements more appropriate for astrochemistry than the existing values. We found that CO2 forms clusters on np-ASW surface even at very low coverages. The binding energies of N2, CO, O2, and CH4 decrease with coverage in the submonolayer regime. Their values at the low coverage limit are much higher than what is commonly used in gas-grain models. An empirical formula was used to describe the coverage dependence of the binding energies. We used the newly determined binding energy distributions in a simulation of gas-grain chemistry for cold cloud and hot core models. We found that owing to the higher value of desorption energy in the sub-monlayer regime a fraction of all these ices stays much longer and up to higher temperature on the grain surface compared to the single value energies currently used in the astrochemical models.