КиHeтикa peкoMбиHaции злэктпoHo B и иoHoB, гeHepиpoBaHHьxч иoHизиp yющиM излyчeHиeM B тBepдьxч yглeBopo дaч

Abstract

The kinetics of photocurrent, I θ, induced by light in the wavelength range λ ≈ 1600 nm in λ-irradiated 3-methylpentane (3MP), methylcyclohexane (MCH) and iso-octane have been studied at 77 K. The decay curve of I θ in iso-octane could be fitted with a second-order law with the rate constant, k p , close to theoretical value, k L , for diffusion-controlled recombination. This decay of I θ was interpreted as recombination of free charges. The decay curves of I in 3MP and MCH did not follow a simple first-order or second-order law; the formally computed value k p ▪ k L . These decays of I θ are assumed to involve the photocurrent component, I g, related to geminate recombination. To describe the kinetics of I g the time dependence of the current due to photoejection of trapped electrons has been discussed in the case of isolated pairs of changes (trapped electrons and positive ions). The current I g N has been computed for the pairs comprising electrons photoejected N times before recombination. It has been shown that the decay curve I g could be fitted by the function Σ N = 2 ∞ Y( N) I g N , where Y(N) ∼ N − 3 2 . For N large the function Y( N) corresponds to the d distribution function for ion-pair lifetimes G(t) ∼ t − 3 2 accepted for liquid hydrocarbons for large t. The distribution function N − 3 2 was applied to describe the published data on time dependences of optical density, D, and quantum yield photobleaching of trapped electrons, and on decay of luminuscence, L r , in irradiated 3MP at 77 K. Good agreement with isothermal decays of D and L, was obtained for the electron lifetime in a trap τ = 26 min.