Primary reactions of localized electrons in rhamnose crystals studied by pulse radiolysis and ESR spectroscopy

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Abstract
The optical absorption spectrum of localized electrons in rhamnose crystals grown from H2O and D2O solutions has been obtained by means of pulse radiolysis. The absorption maximum is at 500 nm, the half‐width is 250 nm, and εG=9000 M−1 cm−1 (100 eV)−1 at 293 K. The decay is first order. The rate constants at 293 K and the activation energies are 6.9×107 s−1 and 4.1 kcal/mol in the protonated crystal and 4.3×107 s−1 and 5.4 kcal/mol in the deuterated crystal. The assignment of the optical spectrum has been made by ESR. In the deuterated crystal irradiated and measured at 67 K the electron is trapped and characterized by a single easily bleachable line with gt1/2?1 h) to be followed by ESR at 77 K in the deuterated compound. The reaction can also be induced by light with λ<700 nm. Reaction mechanisms and the isotope effect are discussed.