Pulse Radiolysis of Crystalline Ice and Frozen Crystalline Aqueous Solutions

Abstract

THE formation of hydrated electrons involves electronic and orientation polarizations. This is quantitatively described by where ΔE is the transfer energy, A is a coefficient, ε_op and ε_s are the optical and the static dielectric constants, respectively. The orientation polarization, which mainly determines the value of ε_s in polar liquids, changes as the reciprocal of the temperature. As the temperature decreases, therefore, the maximum of the absorption band in liquid water shifts to the short-wave region². The formation of a rigid lattice at the point of the phase transition from liquid to ice sharply decreases the mobility of the dipoles. Values measured for fast processes ε_s in equation 1 should be substituted by the values measured in an a.c. field of suitable frequency; for processes involving hydrated electrons, τ ∼ 10⁻⁶–10⁻⁴ sec. At − 10° C, ε is between 3 and 20 if measured at a suitable frequency (10⁶–10⁴ c/s) (ref. 3). Equation 1 then gives ΔE equal to between 1.45 and 0.45 eV, which correspends to a λ_max between 9,000 and 40,000 Å. If this reasoning were correct, the absorption maximum would be expected to shift into the infra-red when the temperature is below 0° C.