Time-resolved conductivity methods

Measurement of the temporal variation of the conductivity after or during injection of charge carriers yields information on the transport properties of the charge carriers involved. 

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Pulse radiolysis, using as time-resolved detection methods optical absorption, luminescence, electrical conductivity or electron spin resonance can be expected to give information on the formation of transient or permanent radiation products and on their movement. 

Photosynthesis. In the photosynthetic process light energy is absorbed by carotenoids and bacteriochlorophylls and transferred to photosynthetic reaction centers. Time-resolved vibrational methods, including transient RR and TR techniques, are well-suited to elucidate the structure and dynamics of the excited (singlet and triplet) states of these chromophores. Nanosecond and picosecond transient RR studies of carotenoid excited states have been conducted by Atkinson and co-workers ... 

In a pulse-radiolysis microwave-conductivity method, the kr value is determined by the time-resolved measurement of microwave conductivity. 

While the first experiments of time-resolved IR spectroscopy were conducted with pulse durations exceeding 10 ps, the improved performance of laser systems now offers subpicosecond (12) to femtosecond (13-15) pulses in the infrared spectral region. In addition, the pump-probe techniques have been supplemented by applications of higher-order methods, e.g., IR photon echo observations (16). 

A separate development of the TRMC techniques was their application to the study of dipolar and excitonic species formed on flash-photolysis of dilute solutions and, more recently, to charge transport and charge separation in thin (aligned) solid films. In the present review we restrict ourselves to results that we have obtained on pulse-irradiated materials, for which the method has become known as the pulse-radiolysis time-resolved microwave conductivity or PR-TBAIC technique. 

The oxidation of alkenes by 804 " has been studied in aqueous acetonitrile solution, using time-resolved (a) optical and (b) conductance methods [45]. 804" was produced in the presence of the alkenes by (i) laser photolysis (20 ns pulse,... 

Subsequently, photoinduced interfacial electron transfer from the conduction band of colloidal Ti02 to dimeric viologen, an electron acceptor, was also examined by picosecond time-resolved methods (Serpone et at., 1987). Electron transfer takes place in the picosecond time domain = 2.5 x 10 s at pH 7.8. The reaction involves consecutive one-electron transfer to give the mono-reduced initially, followed by formation of DV ". In acidic aqueous media (pH 3.5), transient absorption spectra showed that electron transfer does not proceed beyond the formation of the mono-reduced species. 

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