Radiation-induced reactions pulse radiolysis

The electron itself is frequently used as a primary source of radiation, various kinds of accelerators being available for that purpose. Particularly important are pulsed electron sources, such as the nanosecond and picosecond pulse radiolysis machines, which allow very fast radiation-induced reactions to be studied (Tabata et al, 1991). Note that secondary electron radiation always constitutes a significant part of energy transferred by heavy charged particles. For these reasons, the electron occupies a central role in radiation chemistry. 

It is known that more than 30 reactions are needed to reproduce the radiation-induced reactions occurring in pure water. Intensive measurements with a pulse radiolysis method have been done at elevated temperature up to 300°C [25 2], and the temperature dependence of some reactions does not exhibit a straight line but a curved one in Arrhenius plot. These examples are the reactions of the hydrated electron with N2O, NOJ, NO2, phenol, Se04, 8203 , and Mn [33,35], and two examples, egq + NOJ and ejq -i- NOJ, are shown in Fig. 2. The rate constant for the reaction of hydrated electron with NOJ is near diffusion-controlled reaction at room temperature and is increasing with increasing temperature. Above 100°C, the rate does not increase and reaches the maximum at 150°C, and then decreases. Therefore the curve is concave upward in Arrhenius plot. 

The scheme of radiation-induced reactions of CMS, negative electron resist, is proposed as follows on the basis of the present pulse radiolysis data. 

With the development of very high intensity radiation sources, the reactions of the primary species can now be followed directly (16). Both optical spectra and electrical conductivity have been used to follow chemical reactions induced by pulse radiolysis. e aq and OH radicals have optical absorptions that can be easily followed. H atoms cannot be... 

Radiation-induced reactions include photo-induced reactions or those initiated by radicals generated by an electron beam—the pulse radiolysis method. Reactions initiated by a light signal clearly can be of conventional time range or rapid. The latter... 

As described above, recent advances in accelerator technology have enabled the production of very short electron pulses for the study of radiation-induced reaction kinetics. Typically, digitizer-based optical absorbance or conductivity methods are used to follow reactions by pulse radiolysis (Chap. 4). However, the time resolution afforded by picosecond accelerators exceeds the capability of real-time detection systems based on photodetectors (photomultiplier tubes, photodiodes, biplanar phototubes, etc.) and high-bandwidth oscilloscopes (Fig. 8). Faster experiments use streak cameras or various methods that use optical delay to encode high temporal resolution, taking advantage of the picosecond-synchronized laser beams that are available in photocathode accelerator installations. 

Kozawa T, Saeki A, Yoshida Y, Tagawa S. (2002) Study on radiation-induced reaction in microscopic region for basic understanding of electron beam patterning in lithographic process (1) development of subpicosecond pulse radiolysis and relation between space resolution and radiation-induced reactions of onium salt. Jpn J Appl Phys 41 4208-4212. 

It is known that more than 30 reactions are needed to reproduce the radiation-induced reactions occurring in pure water. Intensive measurements with a pulse radiolysis method have been done at elevated temperature up to 300°C [25-42], and the temperature dependence of some reactions does not exhibit a straight line but a curved one in Arrhenius plot. These examples are the reactions of the hydrated electron with N2O, NOJ, NOJ, phenol. 

Another interesting topic concerning radiation-induced reactions in proteins in aqueous solution concerns intramolecular long-distance electron transfer in proteins [85,98,101]. Respective studies were performed using pulse radiolysis... 

An almost complete description of both OH radical-mediated and one-electron oxidation reactions of the thymine moiety (3) of DNA and related model compounds is now possible on the basis of detailed studies of the final oxidation products and their radical precursors. Relevant information on the structure and redox properties of transient pyrimidine radicals is available from pulse radiolysis measurements that in most cases have involved the use of the redox titration technique. It may be noted that most of the rate constants implicating the formation and the fate of the latter radicals have been also assessed. This has been completed by the isolation and characterization of the main thymine and thymidine hydroperoxides that arise from the fate of the pyrimidine radicals in aerated aqueous solutions. Information is also available on the formation of thymine hydroperoxides as the result of initial addition of radiation-induced reductive species including H" atom and solvated electron. 

Basic and applied researches on charged particle and photon-induced reactions of polymers are surveyed. The basic parts are fundamentals of radiation effects on polymers and pulse radiolysis studies on polymers. The intermediate parts are a great diversity of radiation effects on polymers and reaction mechanisms of electron beam (EB) and x-ray resists. The applied parts are economic scale of utilization of radiation and industrial application of radiation to polymers. 

Onium salts have been widely used as an acid generator for photo-, EB, and x-ray resist. In addition, aromatic polymers such as novolak and polyhydroxystyrene have been often used as a base polymer for EB and x-ray resist. The reaction mechanisms in a typical resist system have been investigated by pulse radiolysis [43,52,77-88], SR exposure [79,80,83-85], and product analysis [88]. Figure 6 shows the acid-generation mechanisms induced by ionizing radiation in triphenylsulfonium triflate solution in acetonitrile. The yields of products from electron beam and KrF excimer laser irradiation of 10 mM triphenylsulfonium triflate solution in acetonitrile are shown in Fig. 7 to clarify the... 

Buxton GV, Mulazzani QG, Ross AB (1995) Critical review of rate constants for reactions of transients from metal ions and metal complexes in aqueous solutions. J Phys Ref Data 24 1035-1349 Cheek CH, Swinnerton JW (1964) The radiation-induced chain reaction between nitrous oxide and hydrogen in aqueous solutions. J Phys Chem 68 1429-1432 Christensen H, Sehested K (1980) Pulse radiolysis at high temperatures and high pressures. Radiat Phys Chem 16 183-186... 

Cadet J, Voituriez L, Berger M, Myers LS Jr (1983) Radiation-induced degradation of purine and pyrimidine 2 -deoxyribonudeosides in agueous KBr solutions. Z Naturforsch 38b 1643-1651 Champagne MH, Mullins MW, Colson A-O, Sevilla MD (1991) Electron spin resonance evidence for intra- and intermolecular oo bonding in methionine radicals relative stabilities of S-CI, S-Br, S-N, and S-S three electron bonds. J Phys Chem 95 6487-6493 Chawla OP, Fessenden RW (1975) Electron spin resonance and pulse radiolysis studies of some reactions of S04. J Phys Chem 79 2693-2700... 

Schuchmann MN, von Sonntag C (1988) The rapid hydration of the acetyl radical. A pulse radiolysis study of acetaldehyde in aqueous solution. J Am Chem Soc 110 5698-5701 Schuchmann MN, von Sonntag C, Tsay YH, Kruger C (1981) Crystal structure and the radiation-induced free radical chain- reaction of 2-deoxy-p-D-erythro-pentopyranose in the solid state. Z Naturforsch 36b 726-731... 

Adhikari S, Sprinz H, Brede 0 (2001) Thiyl radical induced isomerization of unsaturated fatty acids determination of equilibrium constants. Res Chem Intermed 27 549-559 Adhikary A, Bothe E, Jain V, von Sonntag C (2000) Pulse radiolysis of the DNA-binding bisbenzimid-azole derivatives Hoechst 33258 and 33342 in aqueous solution. Int J Radiat Biol 76 1157-1166 Akhlaq MS, von Sonntag C (1986) Free-radical-induced elimination of H2S from dithiothreitol. A chain reaction. J Am Chem Soc 108 3542-3544... 

Ellison DH, Salmon GA, Wilkinson F (1972) Nanosecond pulse radiolysis of methanolic and aqueous solutions of readily oxidizable solutes. Proc R Soc Lond A 328 23-36 Erben-Russ M, Bors W, Saran M (1987) Reactions of linoleic acid peroxyl radicals with phenolic antioxidants a pulse radiolysis study. Int J Radiat Biol 52 393-412 Eriksen TE, Fransson G (1988) Radical-induced oxidation of glutathione in alkaline aqueous solution. Radiat Phys Chem 32 163-167... 

Grollmann U, Schnabel W (1980) On the kinetics of polymer degradation in solution, 9. Pulse radiolysis of polyethylene oxide). Makromol Chem 181 1215-1226 Hamer DH (1986) Metallothionein. In Richardson CC, Boyer PD, Dawid IB, Meister A (eds) Annual review of biochemistry. Annual Reviews, Palo Alto, pp 913-951 Held KD, Harrop HA, Michael BD (1985) Pulse radiolysis studies of the interactions of the sulfhydryl compound dithiothreitol and sugars. Radiat Res 103 171-185 Hilborn JW, PincockJA (1991) Rates of decarboxylation of acyloxy radicals formed in the photocleavage of substituted 1-naphthylmethyl alkanoates. J Am Chem Soc 113 2683-2686 Hiller K-O, Asmus K-D (1983) Formation and reduction reactions of a-amino radicals derived from methionine and its derivatives in aqueous solutions. J Phys Chem 87 3682-3688 Hiller K-O, Masloch B, Gobi M, Asmus K-D (1981) Mechanism of the OH radical induced oxidation of methionine in aqueous solution. J Am Chem Soc 103 2734-2743 Hoffman MZ, Hayon E (1972) One-electron reduction of the disulfide linkage in aqueous solution. Formation, protonation and decay kinetics of the RSSR radical. J Am Chem Soc 94 7950-7957... 

Deeble DJ, von Sonntag C (1992) Decarboxylation of 3,4-dihydroxymandelic acid induced by the superoxide radical anion a chain reaction. Int J Radiat Biol 62 105 Deeble DJ, Parsons BJ, Phillips GO (1987) Evidence for the addition of the superoxide anion to the anti- oxidant -propyl gallate in aqueous solution. Free Rad Res Commun 2 351-358 Deeble DJ, Parsons BJ, Phillips GO, Schuchmann H-P, von Sonntag C (1988) Superoxide radical reactions in aqueous solutions of pyrogallol and n-propyl gallate the involvement of phenoxyl radicals. A pulse radiolysis study. Int J Radiat Biol 54 179-193 Denisov ET, Denisova TG (1993) The polar effect in the reaction of alkoxy and peroxy radicals with alcohols. Kinet Catal 34 738-744... 

Janik I, Ulanski P, Flildenbrand K, Rosiak JM, von Sonntag C (2000) Hydroxyl-radical-induced reactions of poly(vinyl methyl ether) a pulse radiolysis, EPR and product study in deoxygenated and oxygenated aqueous solutions. J Chem Soc Perkin Trans 2 2041-2048 Jayson GG, Stirling DA, Swallow AJ (1971) Pulse- and X-radiolysis of 2-mercaptoethanol in aqueous solution. Int J Radiat Biol 19 143-156... 

ScholesG, Willson RL, Ebert M (1969) Pulse radiolysis of agueous solutions of deoxyribonudeotides and of DNA reaction with hydroxy-radicals. Chem Commun 17-18 Schuchmann MN, von Sonntag C (1982) Flydroxyl radical induced oxidation of diethyl ether in oxygenated aqueous solution. A product and pulse radiolysis study. J PhysChem 86 1995-2000 Shragge PC, Michaels FIB, Flunt JW (1971) Factors affecting the rate of hydrated electron attack on polynucleotides. Radiat Res 47 598-611... 

Hankiewicz E (1995) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis II. Reactions of primary radicals with oxidants. Bull Pol Acad Sci Chem 43 41-49 Hankiewicz E (1996) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis - Part III. Consecutive reactions. Radiat Phys Chem 47 61-65 Hankiewicz E (1998) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis. IV. Reactions of primary radicals with reductants. Bull Pol Acad Sci Chem 46 455-464 Hankiewicz E, Bothe E, Schulte-Frohlinde D (1992) Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis, part. I. Transformation reactions of two isomeric OH-adducts. Free Rad Res Commun 16 391-400... 

Pulse radiolysis studies concerning the polymerization as well as the degradation, crosslinking and radiation resistance of polymers are surveyed. Initiation mechanisms of the radiation-induced polymerization of styrene and other monomers are discussed on the basis of the direct measurements of the reaction intermediates. Optical and kinetic data on the short-lived chemical intermediates produced in the solution of polymers and in the rigid polymers are surveyed and discussed with special reference to the degradation mechanism of polymers. 

Application of pulse radiolysis to polymers and polymerization was motivated at first by the success of radiation-induced polymerization as a novel technique for polymer synthesis. It turned out that a variety of monomers could be polymerized by means of radiolysis, but only a little was known about the reaction mechanisms. Early studies were, therefore, devoted to searching for initiators of radiation-induced polymerization such as radicals, anions and cations derived from monomers or solvents. Transient absorption spectra of those reactive intermediates were assigned with the aid of matrix isolation technique. Thus the initiation mechanisms were successfully elucidated by this method. Propagating species also were searched for enthusiastically in some polymerization systems, but the results were rather negative, because of the low steady state concentration of the species of interest. 

It is from these perspectives that we have reviewed the pulse radiolysis experiments on polymers and polymerization in this article. The examples chosen for discussion have wide spread interest not only in polymer science but also in chemistry in general. This review is presented in six sections. Section 2 interprets the experimental techniques as well as the principle of pulse radiolysis the description is confined to the systems using optical detection methods. However, the purpose of this section is not to survey detail techniques of pulse radiolysis but to outline them concisely. In Sect. 3, the pulse radiolysis studies of radiation-induced polymerizations are discussed with special reference to the initiation mechanisms. Section 4 deals with applications of pulse radiolysis to the polymer reactions in solution including the systems related to biology. In Sect. 5 reaction intermediates produced in irradiated solid and molten polymers are discussed. Most studies are aimed at elucidating the mechanism of radiation-induced degradation, but, in some cases, polymers are used just as a medium for short-lived species of chemical interest We conclude, in Sect. 6, by summarizing the contribution of pulse radiolysis experiments to the field of polymer science. 

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