Pulse radiolysis system

Now several picosecond pulse radiolysis systems are operating in Argonne National Laboratory, Brookhaven National Laboratory and University of Tokyo and are under construction in University of Paris South and Waseda University, although only one sub-picopulse radiolysis is operating in Osaka University. 

The experiments were carried out using the subpicosecond pulse radiolysis system [77] described in Sec. 10.2.2 ( Subpicosecond Pulse Radiolysis ). Considering the signal intensity and the degradation of the time resolution, a sample cell with the optical length of 2 mm was mostly used. The sample was saturated by Ar gas to eliminate the scavenging effect by the remaining O2 gas. 

Very intense and sharp near-UV absorption bands due to radical ions of polysilanes [53a,b] and polygermanes [53c] were observed by nanosecond pulse radiolysis. Broad visible and IR absorption spectra due to the radical ions of polysilyne [54] and polygermyne [54] were also observed. Very systematic pulse radiolysis studies on many different kinds of polysilanes [55] have been made by our improved nanosecond pulse radiolysis system over a wide range of... 

Figure 5 Transient absorption spectra of irradiated additive-free solid PMMA containing MMA monomers observed by the authors improved nanosecond pulse radiolysis system over a wide range of temperatures and with the monitoring wavelength region from 300 to 1600 nm.

Details of the picosecond pulse radiolysis system for emission (7) and absorption (8) spectroscopies with response time of 20 and 60 ps, respectively, including a specially designed linear accelerator (9) and very fast response optical detection system have been reported previously. The typical pulse radiolysis systems are shown in Figures 1 and 2. The detection system for emission spectroscopy is composed of a streak camera (C979, HTV), a SIT... 

Figure 1. The schematic diagram of the picosecond pulse radiolysis system for emission spectroscopy.

Rate studies of the reaction between cesium and water in ethylenediamine, using the stopped-flow technique, have been extended to all alkali metals. The earlier rate constant (k — 20 NT1 sec.-1) and, in some cases, a slower second-order process (k — 7 Af"1 sec.-1) have been observed. This is consistent with optical absorption data and agrees with recent results obtained in aqueous pulsed-radiolysis systems. Preliminary studies of the reaction rate of the solvated electron in ethylenediamine with other electron acceptors have been made. The rate constant for the reaction with ethylene-diammonium ions is about 105 NCl sec.-1 Reactions with methanol and with ethanol show rates similar to those with water. In addition, however, the presence of a strongly absorbing intermediate is indicated, which warrants more detailed examination. 

Yoshida, Y., Ueda, T., Kobayashi, H., Tagawa, S. 1993. Studies of geminate ion recombination and formation of excited states in liquid n-dodecane by means of a new picosecond pulse radiolysis system. Nucl. Instr. Meth. Phys. Res. A 327 41 —43. 

Fig. 1. Block diagram of the nanosecond pulse radiolysis system using the Hokkaido University 45 MeV electron linear accelerator...

Pulse radiolysis systems capable of picosecond time resolution use the fine structure of the output from the electron linear accelerator. Electrons in the accelerating tube respond to positive or negative electric field of the radiofrequency, and they are eventually bunched at the correct phase of the radiofrequency. Thus the electron pulse contains a train of bunches or fine structures with their repetition rate being dependent on the frequency of the radiofrequency (350 ps for the S-band and 770 ps for the L-band). 

Very recently Kouchi et al. constructed an ion beam pulse radiolysis system and use it for the study of the LET effect in irradiated polystyrene thin films [106]. The nanosecond pulsed MeV ion beam with the variable repetition rate was obtained by chopping ion beams from a Van de Graaff. Time profiles of the excimer fluorescence from polystyrene thin films, excited by He+ impact, were... 

Direct measurement of short-lived reactive intermediates by time-resolved spectroscopic methods is very important for understanding the detailed mechanisms of radiation effects. Very recently a new ion beam pulse radiolysis system using optical multi-channel detection has been developed. Although the use of ion beam pulse radiolysis for studying the radiation effects of ion beams on polymers was first reported by us [3, 30], the new system is highly modified for investigating ion beam reactions. Electron beam pulse radiolysis was also carried out complementarily. 

In Fig. 5, the schematic diagram of the ion beam pulse radiolysis system with an optical emission spectroscope is also shown. The emission produced by the pulsed ion beam impact is detected through a monochromator by a fast photomultiplier tube (PMT) operated in a counting mode. The time profile of the emission is obtained by a coincident measurement between a photon and a... 

Fig. 5. The schematic diagram of the pulsing system and the ion beam pulse radiolysis system with an optical emission spectroscopy. PMT denotes photomultiplier tube HV, high voltage supply CFD, constant fraction discriminator TAC, time to amplitude converter and PH A, pulse height analyzer. From Ref. 36...

Samples were irradiated by a 10 ps single or 2 ns electron pulse from a 35 MeV linear accelerator for pulse radiolysis studies (17). The fast response optical detection systems of the pulse radiolysis system for absorption spectroscopy (18) is composed of a very fast response photodiode (R1328U, HTV.), a transient digitizer (R7912, Tektronix), a computer (PDP-11/34) and a display unit. The time resolution is about 70 ps which is determined by the rise time of the transient digitizer. 

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. 

Bronskill MJ, Taylor WB, Wolff RK, Hunt JW. (1970) Design and performance of a pulse radiolysis system capable of picosecond time resolution. Rev Sci Instrum 4 333-340. 

Patterson LK, Lilie J. (1974) A computer-controlled pulse radiolysis system. Int J Radiat Phys Chem 6 129-141. 

Fig. 5. Ultrafast pulse radiolysis system at NERL, University of Tokyo.

Grigoryants VM, Lozovoy W, Chemousov YuD, Shebolaev IV, Arutyunov AV, Anisimov OA, Molin YuN. (1989) Pulse radiolysis system with picosecond time resolution referred to Cherenkov radiation. Radiat Phys Chem 34 349-352. 

Yoshida Y, Mizutani Y, Kozawa T, Saeki A, Seki S, Tagawa S, Ushida K. (2001) Development of laser-synchronized picosecond pulse radiolysis system. Radiat Phys Chem 60 313-318. 

Aoki Y, Nakajyo T, Tsimemi A, Yang JF, Okada Y, Yorozu M, Hirose M, Sakai F, Endo A. (2001) Performance of compact pulse radiolysis system using a photocathode RF gun. Res Chem Intermediat 27 689-697. 

Nagai H, Kawaguchi M, Sakaue K, Komiya K, Nomoto T, Kamiya Y, Hama Y, Washio M, Ushida K, Kashiwagi S, Kuroda R. (2007) Improvements in time resolution and signal-to-noise ratio in a compact pico-second pulse radiolysis system. Nucl Instrum Meth B 265 82-86. 

Muroya Y, Watanabe T, Wu G, Li X, Kobayashi T, Sugahara J, Ueda T, Yoshii K, Uesaka M, Katsumura Y. (2001) Design and development of a subpicosecond pulse radiolysis system. Radiat Phys Chem 60 307-312. 

---