TY - JOUR
T1 - Binding energy of molecules on water ice
T2 - Laboratory measurements and modeling
AU - He, Jiao
AU - Acharyya, Kinsuk
AU - Vidali, Gianfranco
N1 - Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.
PY - 2016/7/10
Y1 - 2016/7/10
N2 - 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 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 the 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 binding energy in the submonolayer regime, a fraction of all these ices remains for much longer and up to higher temperatures on the grain surface compared to the single value energies currently used in the astrochemical models.
AB - 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 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 the 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 binding energy in the submonolayer regime, a fraction of all these ices remains for much longer and up to higher temperatures on the grain surface compared to the single value energies currently used in the astrochemical models.
KW - ISM: abundances
KW - ISM: atoms
KW - ISM: molecules
KW - astrochemistry
KW - dust, extinction
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U2 - 10.3847/0004-637X/825/2/89
DO - 10.3847/0004-637X/825/2/89
M3 - Article
AN - SCOPUS:84978536215
SN - 0004-637X
VL - 825
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 89
ER -