On the nature of photo charge carriers in ice

Abstract

A method of photoelectromotive force (PEMF) was developed to find the charge sign, mobility, and lifetime of photo charge carriers in ice generated by photons with energy hν≳6.5 eV. It was determined that the most mobile photo charge carriers are negative ones, with mobility μ increasing from 2×10−3 cm2/V s at T=−10 °C to 4×10−2 cm2/V s at T=−30 °C, and with their lifetime decreasing from 30 to 10 s in the same temperature range. Activation energies of the mobility and the lifetime are Eμ=−0.77 eV and Eτ=0.32 eV, respectively. In addition to the negative photo charge carriers positive ones arise with mobility μ=2.3×10−4 cm2/V s and lifetime τ=26 min at T=−15 °C. We suggest that the negative photo charge carriers in ice are mobile complexes of an electron, vacancy and D-defect (e−+V+D). To take into account a specific mechanism of charge transport in ice, configurational vector Ω, and the generation of complexes (e−+V+D), a reaction of ‘‘autoionization’’ was modified for ice, 2H2O+hν→H3O++OH•int(e−+V+D).