Stroboscopic pulse radiolysis

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... 

The results in this discussion will include those from our laboratory and experiments on electron solvation from other laboratories. The experiments that were done at Argonne made use of the stroboscopic pulse radiolysis technique, which will be discussed below. Experiments from other laboratories have made use of pulse radiolysis and laser photolyis techniques for the measurement of electron solvation. 

The stroboscopic pulse radiolysis with the single bunch electron pulse instead of pulse trains started in Argonne National Laboratory in 1975 [54]. The research fields have been extended by the stroboscopic pulse radiolysis with the picosecond single electron bunch, although most of researches had been limited to hydrated and solvated electrons in the aqueous and alcoholic solutions. This system was unable to study the kinetics of the geminate ion recombination in liquid hydrocarbons until the modification of the Argonne linac in 1983, which made possible the quality measurements of the weak absorption. 

To address the questions of non-homogeneous/spur kinetics, John Hunt and his group at Toronto developed a sub-nanosecond pulse-radiolysis system.In their stroboscopic pulse radiolysis system, they could observe from about 30 to 350 ps after the pulse with a time resolution of about 10 ps. Their results showed no significant decay of the electron between 30 and 350 ps, which was not consistent with the diffusion-kinetic models of spur decay in radiation chemistry. 

Hamill had suggested that there was a precursor of the hydrated electron that could be scavenged and called this species the dry elec-tron. Work by the Hunt group with his stroboscopic pulse radiolysis... 

The stroboscopic pulse radiolysis system described above was modified at Argonne National Laboratory to use a single fine-structure pulse from a 20-MeV L-band linac [150]. This reduced the uncertainty in the age of the primary produets to the width of a fine-structure pulse and allowed kinetic measurements to be extended to 3.5 ns. In practice, the time resolution of absorbance measurements was 100 ps. 

The first picosecond pulse radiolysis experiment was carried out in the late 1960s by the so-called stroboscopic method (generally pomp and probe method) at University of... 

The subpicosecond pulse radiolysis [74,77] detects the optical absorption of short-lived intermediates in the time region of subpicoseconds by using a so-called stroboscopic technique as described in Sec. 10.2.2 ( History of Picosecond and Subpicosecosecond Pulse Radiolysis ). The short-lived intermediates produced in a sample by an electron pulse are detected by measuring the optical absorption using a very short probe light (a femtosecond laser in our system). The time profile of the optical absorption can be obtained by changing the delay between the electron pulse and the probe light. 

Another aspect of pulse radiolysis which has been improved is the pulse duration. For most experiments of interest to the physical organic chemist the common machines with pulse durations of 10 7-10-5 s are quite satisfactory, though for certain reactions, such as those involving protonation, examination on a shorter time scale can be of value. Several accelerators which supply nanosecond pulses are currently in use, but they are employed mostly with microsecond detection systems. Work in the 10-12-10-1° s region has recently become possible by the stroboscopic technique utilizing the fine structure pulses from a linear accelerator (Bronskill et al., 1970). More recently, a system which produces a single pulse of 40 picoseconds has been constructed (Ramler et al., 1975) and utilized for the observation of hydrated electrons at very short times (Jonah et al., 1973). 

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