Low Temperature Physics: 34, 397 (2008); https://doi.org/10.1063/1.2911662 (7 pages)
Физика Низких Температур: Том 34, Выпуск 4-5 (Апрель 2008), c. 496-503    ( к оглавлению , назад )

Electron attachment to atomic hydrogen on the surface of liquid 4He

Toshikazu Arai

Research Center for Low Temperature and Materials Sciences, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
E-mail: toshikaz@scphys.kyoto-u.ac.jp

Hideki Yayama

Department of Physics, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka, 810-8560, Japan

Kimitoshi Kono

RIKEN, Low Temperature Physics Laboratory, Hirosawa 2-1, Wako-shi, Saitama, 351-0198, Japan

Received November 6, 2007


We demonstrate a possibility that helium surface electrons at cryogenic temperatures can be used as a new source of very low energy electrons. Since both electrons (e-) and hydrogen atoms (H) are bound on liquid helium surface, two-dimensional mixture gas of these two species is available on the surface. We found that low energy collision of e- and H drives electron attachment to form a negative hydrogen ion (H-) in the mixture. From our temperature dependence measurement of the reaction rate, it was found that another H atom participate in the reaction. Namely, the reaction is expressed as H + H + e- + H- + H. Possible reaction mechanisms are discussed in terms of direct three-body process and dissociative attachment process. Measurements in applied magnetic field (B) show that the reaction rate coefficient is suppressed as ~ B-2. This implies that electron spin singlet collision is relevant for electron attachment.

PACS: 67.63.Gh Atomic hydrogen and isotopes;
PACS: 67.25.–k 4He;
PACS: 68.03–g Gas-liquid and vacuum-liquid interfaces.

Key words: surface state electrons, atomic hydrogen, electron attachment.