title: Experimental approach to nonenergetic physicochemical processes on icy grains

authors: Naoki Watanabe

abstract: In the core of dense cloud where radiation field is very weak, nonenergetic physicochemical processes without photons and ions become important for chemical evolution on icy grains. In this context, we have performed a series of experiments regarding tunneling reactions, diffusion, and conversion of nuclear spin temperature mainly for hydrogen on cryogenic ice surfaces as listed below. From among these topics, I will present the results of experiments on tunneling reactions and surface diffusion of hydrogen atom on ice and those implications to molecular formation on icy grains.
The list ofsome our studies relevent to chemical evolution on icy grains.
1. Tunneling reactions of hydrogen and deuterium atoms on ice to produce water, formaldehyde, methanol and those deuterad species.
2.  Diffusion process of hydrogen and deuterium atoms on ice at very low temperatures.
3.  Reactions of cold OH radical with CO to produce CO2 and H2CO3 .
4.  Spin temperatures of H2 and H2O molecules on ice.
5.  Reaction of hydrogen and nitrogen atoms to produce NH3.
6.  Formation of water molecule by tunneling reaction of hydrogen molecules with cold OH.