Surface processes of hydrogen on amorphous solid water (ASW) play an important role in chemical evolution on cosmic ice dust. To understand hydrogen chemistry on ASW, we have performed a series of experiments and found quantum tunneling is a key for the following processes under the environments of molecular clouds: (1) formation of abundant molecules such as H2O, H2CO, and CH3OH, (2) deuterium fractionation of water, formaldehyde, methanol and methylamine. In the next stage, we are investigating the variation of spin temperature of H2 and the diffusion of H atoms on the surface of ASW, which are essential processes previous to tunneling reactions. I will talk about the results of recent experiments regarding these processes. It was found that the H-atom diffusion on ASW is not simple in contrast to that on a crystalline surface. The diffusion mechanisms on ice will be discussed in various conditions.

Diffusion of hydrogen atom on amorphous solid water:Thermal or tunneling?

247th National Meeting (2014)

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