Study on the Tunneling Reaction of H Atoms with a Solid Thin Film of C3H6 at 10 K

Abstract

The reaction of the solid thin film of propene (C 3 H 6 ) deposited on the silicon substrate at 10 K with cold H atoms (∼27 K) sprayed over the solid films was studied. Propane and 2-methylpentane were found to be the majorand minor reaction products, respectively. The rate for the formation of C 3 H 8 increased steeply with a decrease of temperature from 35 to 10 K. This is the general trend for the low-temperature tunneling reactions investigated in our laboratory. With an increase of temperature from 40 to 55 K, the yield of C 3 H 8 showed a slow increase. This may be due to the replenishment of the reactant C 3 H 6 molecules to the surface above ∼40 K (i.e., solid-phase diffusion). The yield of C 3 H 8 from C 3 H 6 was lower than that of C 2 H 6 from C 2 H 4 . This may be due either to the hindrance of the proximity approach of the H atom to the C 3 H 6 double bond by the presence of the methyl group and/or to the annihilation of the H atoms by the H-atom abstraction reaction with the reaction product C 3 H 8 to form the s-C 3 H 7 radical on the surface of the solid film.