First Observation of Tunneling Diffusion of Hydrogen Atoms on the Surface of Very-Low-Temperature Water Ice

Experimental equipment developed at the Institute of Low Temperature Science and used in the present research.

First demonstration of tunneling diffusion of hydrogen atoms on the surface of very-low-temperature water ice.

Clarification of the behavior of hydrogen atoms on the surface of water ice microparticles floating in space.

Establishment of a new experimental method for comparing the diffusion rates of deuterium atoms and hydrogen atoms.

Overview
It is believed that, on microparticles of water ice floating in space, hydrogen atoms that have adhered in the vacuum move around on the surface of the ice and collide with other atoms and molecules to form a variety of molecules, including organic molecules. It has been theoretically predicted that, in the very-low-temperature environment of space, hydrogen atoms move around much faster than usual on the ice surface (tunneling diffusion), as a result of the quantum tunneling effect that is unique to very low temperatures (the phenomenon whereby the wave nature of particles becomes prominent and they can go through energy barriers). However, due to the experimental difficulty, research to demonstrate this has not been performed. By using a novel method, the present research has succeeded for the first time in experimentally observing this tunneling diffusion.