Journal Article Surface Temperature Dependence of Hydrogen Ortho-Para Conversion on Amorphous Solid Water

Ueta, Hirokazu  ,  Watanabe, Naoki  ,  Hama, Tetsuya  ,  Kouchi, Akira

116 ( 25 )  , p.253201 , 2016-06-23 , American Physical Society (APS)
The surface temperature dependence of the ortho-to-para conversion of H-2 on amorphous solid water is first reported. A combination of photostimulated desorption and resonance-enhanced multiphoton ionization techniques allowed us to sensitively probe the conversion on the surface of amorphous solid water at temperatures of 9.2-16 K. Within a narrow temperature window of 8 K, the conversion time steeply varied from similar to 4.1 x 10(3) to similar to 6.4 x 10(2) s. The observed temperature dependence is discussed in the context of previously suggested models and the energy dissipation process. The two-phonon process most likely dominates the conversion rate at low temperatures.

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