Microwave pulse radiolysis

Warman JM, de Haas MP. (1988) The use of COj gas as an in-situ dosimeter for DC and microwave pulse-radiolysis conductivity experiments. Radiat Phys Chem 32 31-36. 

The first experimental measurements of the time dependence of the hydrated electron yield were due to Wolff et al. (1973) and Hunt et al. (1973). They used the stroboscopic pulse radiolysis (SPR) technique, which allowed them to interpret the yield during the interval (30-350 ps) between fine structures of the microwave pulse envelope (1-10 ns). These observations were quickly supported by the work of Jonah et al. (1973), who used the subharmonic pre-buncher technique to generate very short pulses of 50-ps duration. Allowing... 

Warman JM, de Haas MP, Dicker G, Grozema FC, Ptris J, Debije MG (2004) Charge mobilities in organic semiconducting materials determined by pulse-radiolysis time-resolved microwave conductivity 7c-bond-conjugated polymers versus tc—tc-stacked discotics. Chem Mater 16 4600... 

The authors thank a number of collaborators for their excellent collaboration, particularly Dr. N. Kouchi. They also appreciate the early contribution to and the continuous development of the pulse radiolysis microwave conductivity/cavity technique by the late Dr. H. Shimamori. 

Electron attachment to solutes in nonpolar liquids has been studied by such techniques as pulse radiolysis, pulse conductivity, microwave absorption, and flash (laser) photolysis. A considerable amount of data is now available on how rates depend on temperature, pressure, and other factors. Although further work is needed, some recent experimental and theoretical studies have provided new insight into the mechanism of these reactions. To begin, we consider those reactions that show reversible attachment-detachment equilibria and therefore provide both free energy and volume change information. 

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

TC/BG BC/BG SC/BG BC/TG PR-TRMC Top contact/bottom gate Bottom contact/bottom gate Sandwich contact/bottom gate Bottom contact/top gate Pulse-radiolysis time-resolved microwave conductivity technique... 

Measured with the pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique... 

So far the microwave electron linear accelerator is the most suitable for this purpose. In this accelerator electrons are injected into an evacuated cylindrical waveguide in which pulsed radiofrequency of several megawatts from a klystron oscillator travels. Electrons enter the radiofrequency field at the correct phase are accelerated to a velocity close to that of light. By means of gun control, electrons are injected only during the radiofrequency pulse, and thus the electron pulses of several nanosecond duration, useful for conventional nanosecond or microsecond pulse radiolysis, are produced. 

Let us now examine the two minor disadvantages of the laser time-resolved experiments which we mentioned briefly. The low radical concentration normally encountered in such experiments makes evaluation of E-A-type polarization difficult. In fact, even when the radical concentration is not a problem, as in pulse radiolysis study, the time profile has to be fitted to obtain the enhancement factor (124). Another aspect in the time-resolved study is that the experiments have to be repeated at different microwave power levels, as the true intrinsic P or V can only be obtained by extrapolation to zero power. Ironically, these two problems can be overcome readily in semi-steady-state experiments using a conventional slow-response spectrometer. 

A History of Pulse-Radiolysis Time-Resolved Microwave Conductivity (PR-TRMC) Studies... 

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. 

Warman JM. (1982) The microwave absorption technique for studying ions and ionic processes. In Baxendale JH, Busi F. (eds.), The Study rfFast Processes and Transient Species by Electron Pulse Radiolysis, pp. 129-161. Reidel, Dordrecht. 

Warman JM, Gelinck GH, de Haas MP. (2002) The mobility and relaxation kinetics of charge carriers in molecular materials studied by means of pulse-radiolysis time-resolved microwave conductivity Dialkoxy-substituted phenylene-vinylene polymers. J Phys Condensed Matter 14 9935-9954. 

Shimamori H, Tatsumi Y, Ogawa Y, Sunagawa T. (1992) Low-energy electron attachment to molecules studied by pulse-radiolysis microwave-cavity technique combined with microwave heating. J Chem Phys 97 6335-6347. 

Warman JM, de Haas MP, Pichat P, Serpone N. (1991) Effect of isopropyl alcohol on the surface localization and recombination of conduction-band electrons in Degussa P25 TiOj. A pulse-radiolysis time-resolved microwave conductivity study. JPhys Chem 95 8858-8861. 

A historical perspective on these developments is given in the first chapter by Jonah. Janata offers a detailed account of the key technique of electron pulse radiolysis, then firmly placed on the modern stage of ultrafast techniques in the chapter by Belloni et al. By far the most common detection scheme is that of transient optical absorption, however chapters by Warman and de Haas (on microwave conductivity) and Le Caer et al. (on infrared spectroscopy) illustrate alternative approaches. Others, not explicitly addressed, but key to... 

The new accelerator at Brookhaven is based on an RF photocathode gun with one or more resonant cavities in which microwaves create transient electric fields up to 1 MeV cm [104], A pulse of laser light is used for generating photoelectrons which are accelerated to 9 MeV in a distance of 30 cm. The laser pulse can also be used as the analyzing light source this means it is closely synchronized with the electron pulse. The time resolution of the electron pulse is therefore that of the laser pulse, so that subpicosecond pulse radiolysis is possible. A similar system is planned at Argonne National Laboratory [146],... 

Van de Craats et al. used the pulse-radiolysis time resolved microwave conductivity (PR-TRMC) technique to study the charge-transport properties of [ (Ci2H250)gPc 2Lu]. Their results showed an increase in charge carrier mobility at the crystalline solid to Col mesophase... 

PS (polystyrene) 518, 519, 530 PTAA (poly(triarylamine)) 320 PTCDA (perylene tetracarboxilic acid dianhydride) 51, 173 ff, 223 ff p-type transistors 10 pulse radiolysis time resolved microwave conductivity (PR-TRMC) 107 ff. purification 541 ff... 

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