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The imaging reactions of resist materials used for nano-patterning have become radiation-chemical reactions, with the shortening of wavelengths of the exposure light sources in lithography systems. The most widely used patterning materials in industrial lithography are chemically amplified resists (CAR). Understanding the deprotonation mechanism of ionized polymers (radical cations) is important for acid generation in CARs. In this study, the dynamics of radical cations in poly(4-hydroxystyrene) (PHS)–type resist polymers, partially and totally protected by tert-butoxycarbonyl (t-BOC) groups, are investigated using a combination of electron pulse radiolysis experiments, acid yield measurements, and quantum chemical calculations. The t-BOC(oxy) group exhibits π-electron-donating behavior in the monomer cation but changes to electron-accepting behavior in the polymer cation, owing to the interaction between substituents. The destabilization of radical cations due to decreased intramolecular charge resonance may contribute to the high deprotonation efficiency of t-BOC-capped PHS polymers. [ABSTRACT FROM AUTHOR]

The flexible waste management (FWM) system has been proposed in order to apply the partitioning and transmutation (P&T) technology for minor actinides (MA) to the current high-level liquid waste (HLLW). This system consists of HLLW calcination to produce easy-to-dissolve granule; its temporary storage is required until the P&T technology deployment and re-dissolution of the granule to remove MA from HLLW after the future P&T technology deployment. The fundamental experiments were conducted to clarify the applicability of FWM system to the current HLLW, and the results indicate the technological validity of the system. The evaluations were carried out for the reduction of storage amount, potential radiotoxicity, and repository area of high-level waste. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) composite aerogels were synthesized by the radiation reduction of graphene oxide (GO) with the assistance of Eu3+, which demonstrated excellent adsorption performance for diverse organic pollutants. Eu3+ promoted the formation of the gel by inducing the pre-assembly of GO so that the required pH range for synthesizing the rGO aerogel by radiation reduction was broadened and the minimum absorbed dose was also reduced. At pH 2, the Eu3+-induced pre-assembly fabricated more mesopores and enlarged the specific surface area of the obtained hierarchically porous rGO-Eu composite aerogel, which enabled the high-capacity (81–395 g g−1) and ultrafast removal of organic solvents. The different effects of organic solvents on the unique fluorescence emission of Eu(III) also allowed the in situ detection of certain organic solvents such as pyridine. At pH 6, Eu3+ enhanced the reduction of GO by capturing more hydrated electrons, the most reductive species produced by water radiolysis, and synergistically reduced GO. The obtained rGO-Eu composite aerogel with a high reduction degree, demonstrated outstanding adsorption capacities for various anionic organic dyes (40.5–1572.5 mg g−1) owing to the strong π–π interaction and electrostatic attraction. Benefitting from high reduction, it demonstrated adsorption capacity for cationic dyes (97.3–1367.6 mg g−1) comparable to other reported graphene-based aerogels. The rGO-Eu aerogel prepared by radiation reduction might be suitable as a broad-spectrum adsorbent for organic pollutants. [ABSTRACT FROM AUTHOR]

Metal oxide nanocluster resists are a promising candidate for enabling the high-volume production of semiconductor devices with high-numerical-aperture extreme ultraviolet exposure tools. In this study, the sensitization mechanism of metal oxide nanocluster resists was investigated by focusing on the radiation-induced reactions of carboxylic acid ligands. Radiolytic products in various solutions of unsaturated carboxylic acids, aromatic carboxylic acids, and saturated carboxylic acids were analyzed by electrospray ionization mass spectrometry, high-performance liquid chromatography, and dynamic light scattering. The conditions of the solutions were selected to control reaction paths of intermediates. The major reaction paths induced by ionizing radiation were clarified. The obtained results suggest that the generation of bridging ligands is essential to the sensitization of metal oxide nanocluster resists. Both low-energy electrons and radical cations can trigger dimerization. The diffusion of small radicals should be suppressed to prevent dimerization at undesired places. [ABSTRACT FROM AUTHOR]

Metal oxide nanocluster resists have recently attracted considerable attention for use in extreme ultraviolet lithography. To obtain sophisticated guidelines for material design, it is necessary to understand well the radiation-induced chemical reaction scheme including the insolubilization mechanism. In this study, the production of CO2, which is considered to be one of the end products of treatment with an ionizing radiation, was investigated for eight types of carboxylic acid under various conditions using γ-rays (60Co) as a radiation source. The amount of CO2 produced was measured by gas chromatography. GCO2 (/100 eV), which indicates decarboxylation efficiency, was evaluated. CO2 was generated through electron addition, hole transfer, and hydroxyl radical addition to the molecular and ionic forms of carboxylic acids. The dependences of GCO2 on reaction partners were clarified. The dependences of GCO2 on the molecular structure and dissociative state of carboxylic acids were also clarified. [ABSTRACT FROM AUTHOR]

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Metal oxide nanocluster resists have recently attracted considerable attention for use in extreme ultraviolet lithography. In this study, radiation-induced reactions of carboxylic acids used as the ligands of metal oxide nanocluster resists were investigated using a pulse radiolysis method. Upon the irradiation of the aqueous solutions of calboxylic acids with an electron beam, radical dianions of carboxylates were generated under the basic condition. From the comparison between pulse radiolyses under acidic and basic conditions, the kinetics of the radical dianions was clarified. For aromatic carboxylates, anion radicals of carboxylic acids were generated through the reaction of their dianions with H2O. For unsaturated carboxylates, their radicals were generated through the reaction of their radical dianions with H2O. The carboxylic anions and vinyl groups were protonated for dianions of aromatic and unsaturated carboxylates, respectively. The proton dynamics control is important for the stable performance of metal oxide nanocluster resists. [ABSTRACT FROM AUTHOR]

The optical absorption spectra of the hydrated electron (eaq-) in supercritical (heavy) water (SCW) are measured by electron pulse radiolysis techniques as a function of water density at three temperatures of 380, 390, and 400 °C, and over the density range of ∼0.2–0.65 g/cm3. In agreement with previous work, the position of the eaq- absorption maximum (EAmax) is found to shift slightly to lower energies (spectral “redshift”) with decreasing density. A comparison of the present EAmax-density data with other measurements already reported in the literature in subcritical (350 °C) and supercritical (375 °C) water reveals that at a fixed pressure, EAmax decreases monotonically with increasing temperature in passing through the phase transition at tc. By contrast, at constant density, EAmax exhibits a minimum as the water passes above the critical point into SCW. These behaviors are explained in terms of simple microscopic arguments based on the crucial role played by local density and configurational fluctuations (associated with criticality) in providing pre-existing polymeric clusters, which act as trapping sites for electrons. [ABSTRACT FROM AUTHOR]

It is generally considered that the pre-solvated electron and the solvated electron reacting with a solute yield the same product. Silver cyanide complex, Ag(CN)2−, is used as a simple probe to demonstrate unambiguously the existence of a different reduction mechanism for pre-hydrated electrons. Using systematic multichannel transient absorption measurements at different solute concentrations from millimolar to decimolar, global data analysis and theoretical calculations, we present the dissociative electron attachment on Ag(CN)2−. The short-lived silver complex, Ag0(CN)22−, formed by hydrated electron with nanosecond pulse radiolysis, can be observed at room temperature. However, at higher temperatures only the free silver atom, Ag0, is detected, suggesting that Ag0(CN)22− dissociation is fast. Surprisingly, pulse radiolysis measurements on Ag(CN)2− reduction, performed by a 7 ps electron pulse at room temperature, show clearly that a new reduced form of silver complex, AgCN−, is produced within the pulse. This species, absorbing at 560 nm, is not formed by the hydrated electron but exclusively by its precursor. DFT calculations show that the different reactivity of the hydrated and pre-hydrated electrons can be due to the formation of different electronic states of Ag0(CN)22−: the prehydrated electron can form an excited state of this complex, which mainly dissociates into Ag0CN− + CN−. [ABSTRACT FROM AUTHOR]

We measured transient absorption in α-AlO after pulsed electron beam irradiation to analyze the relaxation process of excited states. We used two measurement systems to obtain transient absorption in nanosecond and picosecond time scales. In the nanosecond time scale, we observed a band at 610 nm in addition to a shoulder at 420 nm. This observation is consistent with that in a previous paper, and these bands are attributed to Al interstitials according to the paper. The decay behavior of these bands was significantly different in the picosecond time scale. The difference in the decay kinetics strongly suggests that the band at 610 nm and the shoulder at 420 nm are attributed to two kinds of Al interstitials. [ABSTRACT FROM AUTHOR]

The formation of a HṖ atom in liquid water from the reaction of a hydrated electron with a hydronium cation is a very challenging subject in chemical processes. Here picosecond pulse radiolysis measurements are performed at elevated temperatures, up to 350 °C, of acidic H2O and D2O solutions (up to 0.1 mol L−1 HClO4) with the aim of investigating several issues related to this reaction. First, the red shift of the solvated electron absorption band in D2O with increasing temperature is found to be affected by the presence of D3O+ in solution. The modified absorption spectra demonstrate the formation of a transient pair between D3O+ and solvated electrons at elevated temperature (200–250 °C) when the concentration of D3O+ is higher than 0.05 mol L−1. For higher temperatures at 300 and 350 °C when the rate constant is almost diffusion controlled, the pair is no longer observable. Second, the presolvated electron in D2O is not scavenged up to 250 °C in solution containing 0.1 mol L−1 D3O+. Third, the decays in the picosecond range obtained under different conditions show that the rate constants are strongly affected by the temperature and by ionic strength. The model with an equation of log(k/k0) = 2A(I)0.5/1 + b(I)0.5 gives a good fit of the experimental results by taking into account the variation of ionic strength, I, and, in particular, by considering the temperature dependence of the constant A. [ABSTRACT FROM AUTHOR]

The radiation-induced reactions of a water-soluble coumarin derivative, coumarin-3-carboxyl acid (C3CA), have been investigated in aqueous solutions by pulse radiolysis with a 35 MeV electron beam, final product analysis following 60Co γ-irradiations and deterministic model simulations. Pulse radiolysis revealed that C3CA reacted with both hydroxyl radicals (•OH) and hydrated electrons (e− aq) with near diffusion-controlled rate constants of 6.8 × 109 and 2.1 × 1010 M−1 s−1, respectively. The reactivity of C3CA towards O2• − was not confirmed by pulse radiolysis. Production of the fluorescent molecule, 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA), was confirmed by final product analysis with a fluorescence spectrometer coupled to a high performance liquid chromatography (HPLC) system. Production yields of 7OH-C3CA following 60Co γ-irradiations depended on the irradiation conditions and ranged from 0.025 to 0.18 (100 eV) −1. Yield varied with saturating gas, additive and C3CA concentration, implying the presence of at least two pathways capable of providing 7OH-C3CA as a stable product following the scavenging reaction of C3CA with •OH, including a peroxidation/elimination sequence and a disproportionation pathway. A reaction mechanism for the two pathways was proposed and incorporated into a deterministic simulation, showing that the mechanism can explain experimentally measured 7OH-C3CA yields with a constant conversion factor of 4.7% from •OH scavenging to 7OH-C3CA production, unless t-BuOH was added. [ABSTRACT FROM AUTHOR]

The oxidation processes of the radiation-generated, three-electron-bonded intermediates AcMet 2 [S∴S] + and AcMet [S∴Br] were investigated by pulse radiolysis via their reactions with tryptophan (TrpH). These intermediates were derived from N-acetyl-methionine amide ( N-AcMetNH 2) and N-acetyl-methionine methyl ester ( N-AcMetOMe). The bimolecular rate constant k of the reaction between each intermediate and l-tryptophan (TrpH) was measured. For N-AcMetNH 2, k for the reaction of AcMet 2 [S∴S] + with TrpH were 3.4 × 10 8 and 2.2 × 10 8 dm 3 mol −1 s −1 at pH = 1 and 4.5, respectively. For N-AcMetOMe, k for the reaction of AcMet 2 [S∴S] + with TrpH were 4.0 × 10 8 and 2.8 × 10 8 dm 3 mol −1 s −1 at pH 1 and 4.5, respectively. The rate constants for the intermolecular transformation of Met [S∴Br] into TrpH + or Trp were also estimated. For N-AcMetNH 2, k for the reaction of AcMet 2 [S∴Br] with TrpH were 2.6 × 10 8 and 3.3 × 10 8 dm 3 mol −1 s −1 at pH 1 and 4.5, respectively. Related mechanisms were discussed. [ABSTRACT FROM AUTHOR]

The flavonolignans (silybin and analogues) are important natural compounds with multiple biological activities operating at various cell levels. Many of these effects are connected with their radical scavenging activities. In the present study, free-radical scavenging and antioxidant activities of four natural flavonoids, namely silybin, naringenin, naringin, and hesperetin, have been studied using nanosecond pulse radiolysis techniques. The kinetics and mechanisms of the reactions of silybin and analogues with various oxidizing radicals (such as •OH,N3•, CCl3OO•, SO4•−) have been investigated. Furthermore, the transient species has been assigned and radical scavenging rate constants have also been measured. Moreover, the structure-activity relationships between chemical structures of the flavonoids and their radical scavenging activities are further analayzed by theoretical calculation. Combined our previous observation of the fast reparation of DNA damage and efficient DNA protection against radiation damage in vitro, it can be confirmed that test flavonoids are promising molecules to be used for their potential antioxidant properties. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 590-597, 2011 [ABSTRACT FROM AUTHOR]

Silybin (extracted from Silybum marianum) is the major active constituent of silymarin which possesses a wide range of medicinal properties. These properties may be, in part, due to the potent scavenging capacity of oxidizing free radicals. In this context, scavenging radicals (hydroxyl, azide, dibromide anion radicals, nitrite, carbonate, etc.) of silybin have been studied to understand the mechanistic aspects of its action against free radicals. The transients produced in these reactions have been assigned and the rate constants have been measured by pulse radiolysis techniques. Reduction potential determined both by cyclic voltammetry gave a value 0.62±0.02 V vs NHE at pH 9. Quantum chemical calculations have been performed to further confirm the different activities of individual hydroxyl groups with the difference of heat of formation. Moreover, silybin also protected plasmid pUC18 DNA from soft X-ray radiation which induced strand breaks. These results are expected to be helpful for a better understanding of the anti-oxidative properties of silybin. [ABSTRACT FROM AUTHOR]

We introduce experimental systems which use accelerators to evaluate scintillation properties such as scintillation intensity, wavelength, and lifetime. A single crystal of good optical quality is often unavailable during early stages in the research and development (R&D) of new scintillator materials. Because of their beams’ high excitation power and/or low penetration depth, accelerators facilitate estimation of the properties of early samples which may only be available as powders, thin films, and very small crystals. We constructed a scintillation spectrum measurement system that uses a Van de Graaff accelerator and an optical multichannel analyzer to estimate the relative scintillation intensity. In addition, we constructed a scintillation time profile measurement system that uses an electron linear accelerator and a femtosecond streak camera or a microchannel plate photomultiplier tube followed by a digital oscilloscope to determine the scintillation lifetimes. The time resolution is approximately 10 ps. The scintillation spectra or time profiles can be obtained in a significantly shorter acquisition time in comparison with that required by conventional measuring systems. The advantages of the systems described in this study can significantly promote the R&D of novel scintillator materials. [ABSTRACT FROM AUTHOR]

A re-examination of our Monte-Carlo modeling of the radiolysis of liquid water by low linear-energy-transfer (LET ~ 0.3 keV µm[sup –1] ) radiation is undertaken herein in an attempt to reconcile the results of our simulation code with recently revised experimental hydrated electron (e[sup –] [sub aq] ) yield data at early times. The thermalization distance of subexcitation electrons, the recombination cross section of the electrons with their water parent cations prior to thermalization, and the branching ratios of the different competing mechanisms in the dissociative decay of vibrationally excited states of water molecules were taken as adjustable parameters in our simulations. Using a global-fit procedure, we have been unable to find a set of values for those parameters to simultaneously reproduce (i) the revised e[sup –] [sub aq] yield of 4.0 ± 0.2 molecules per 100 eV at "time zero" (that is, a reduction of ~20% over the hitherto accepted value of 4.8 molecules per 100 eV), (ii) the newly measured e[sup –] [sub aq] decay kinetic profile from 100 ps to 10 ns, and (iii) the time-dependent yields of the other radiolytic species H[sup •] , [sup •] OH, H[sub 2] , and H[sub 2] O[sub 2] (up to ~1 µs). The lowest possible limiting "time-zero" yield of e[sup –] [sub aq] that we could in fact obtain, while ensuring an acceptable agreement between all computed and experimental yields, was ~4.4 to 4.5 molecules per 100 eV. Under these conditions, the mean values of the electron thermalization distance and of the geminate electron–cation recombination probability, averaged over the subexcitation electron "entry spectrum," are found to be equal to ~139 Å and ~18%, respectively. These values are to be compared with those obtained in our previous simulations of liquid water radiolysis, namely ~88 Å and ~5.5%, respectively. Our average electron thermalization distance is also to be compared with the typical size (~64–80 Å) of the initial hydrated electron distributions estimated in current deterministic models of "spur" chemistry. Finally, our average probability for geminate electron–cation recombination agrees well with an estimated value of ~15% recently reported in the literature. In conclusion, this work shows that an adaptation of our calculations to a lower hydrated electron yield at early times is possible, but also suggests that the topic is not closed. Further measurements of the e[sup –] [sub aq] yields at very short times are needed. Key words: liquid water, radiolysis, electron–cation geminate recombination, electron thermalization distance, hydrated electron (e[sup –] [sub aq] ), e[sup –] [sub aq] decay kinetics, time-dependent molecular and radical yields, Monte-Carlo simulations.Nous avons réexaminé le code Monte-Carlo que nous avons développé précédemment pour simuler la radiolyse de l'eau liquide par des rayonnements à faible transfert d'énergie linéique (TEL ~ 0,3 keV µm[sup –1] ) afin de voir s'il est possible de réconcilier les résultats de notre code avec les données expérimentales récemment révisées du rendement en électrons hydratés (e[sup –] [sub aq] ) à temps courts. Les paramètres ajustables utilisés dans nos simulations sont la distance de thermalisation des électrons de subexcitation, la section efficace de recombinaison des électrons avec leurs cations parents de l'eau avant thermalisation et les rapports de branchement des différents mécanismes intervenant lors de la dissociation des états excités vibrationnels des molécules d'eau. En utilisant une procédure d'ajustement global, nous n'avons pas réussi à trouver un jeu de valeurs de ces paramètres permettant de reproduire simultanément : (1) le rendement révisé en e[sup –] [sub aq] de 4,0 ± 0,2 molécules par 100 eV à « temps zéro » (c'est-à-dire, une réduction de ~20 % par rapport à la valeur acceptée jusqu'ici de 4,8 molécules par 100 eV), (2) le profil cinétique de déclin des e[sup –] [sub aq] nouvellement mesuré entre 100 ps et 10 ns et (3) les rendements en fonction du temps des autres espèces radiolytiques H[sup •] , [sup •] OH, H[sub 2] et H[sub 2] O[sub 2] (jusqu'à ~1 µs). En fait, le rendement le plus faible possible en e[sup –] [sub aq] que nous avons réussi à obtenir à « temps zéro », tout en veillant à garder un accord acceptable entre tous les rendements expérimentaux et calculés, s'élève à ~4,4–4,5 molécules par 100 eV. Dans ces conditions, les valeurs de la distance de thermalisation des électrons et de la probabilité de recombinaison géminée électron–cation, moyennées en tenant compte du spectre énergétique des électrons de subexcitation, ont été trouvées respectivement égales à ~139 Å et ~18 %. Ces valeurs sont à comparer avec celles obtenues dans nos simulations antérieures de la radiolyse de l'eau liquide, à savoir, ~88 Å et ~5,5 %, respectivement. Notre valeur moyenne de la distance de thermalisation des électrons est aussi à comparer avec la taille typique (~64–80 Å) des distributions initiales d'électrons hydratés déduites des modèles déterministes actuels de la chimie des « grappes ». Enfin, notre probabilité moyenne de recombinaison géminée électron–cation s'accorde bien avec une valeur estimée de ~15 % rapportée récemment dans la littérature. En conclusion, ce travail montre qu'une adaptation de nos calculs à un rendement plus faible en électrons hydratés à temps courts est possible, mais suggère aussi que le sujet n'est pas clos. D'autres mesures des rendements en e[sup –] [sub aq] à temps courts s'avèrent nécessaires.Mots clés : eau liquide, radiolyse, recombinaison géminée électron–cation, distance de thermalisation de l'électron, électron hydraté (e[sup –] [sub aq] ), cinétique de déclin des e[sup –] [sub aq] , rendements radicalaires et moléculaires dépendants du temps, simulations Monte-Carlo. [ABSTRACT FROM AUTHOR]

Transient radicals (hydrated electron, (SCN)[sub 2][sup .-] and CO[sub 3][sup .-]) formed in supercritical water have been observed by the pulse radiolysis technique. The change of spectra of these radicals with temperature has been measured. It was found that the spectra and absorption coefficients of the radicals, e[sup -][sub aq] and (SCN)[sub 2][sup .-], are strongly dependent on the temperature of the water. Since it was found that the absorption spectrum and molar absorption coefficient of CO[sub 3][sup .-] radical seem to be almost independent of temperature, G-values of OH and e[sup -][sub aq] could be derived. Then, the absolute values of the absorption coefficients for the radicals could be calculated. The G-values of the radical products in water radiolysis tend to increase with increasing temperature up to 400°C. Based on the above observation, radiolysis of supercritical water is discussed. [ABSTRACT FROM AUTHOR]

Damage to DNA via dissociative electron attachment has been well-studied in both the gas and condensed phases; however, understanding this process in bulk solution at a fundamental level is still a challenge. Here, we use a picosecond pulse of a high energy electron beam to generate electrons in liquid diethylene glycol and observe the electron attachment dynamics to ribothymidine at different stages of electron relaxation. Our transient spectroscopic results reveal that the quasi-free electron with energy near the conduction band effectively attaches to ribothymidine leading to a new absorbing species that is characterized in the UV-visible region. This species exhibits a nearly concentration-independent decay with a time constant of ~350 ps. From time-resolved studies under different conditions, combined with data analysis and theoretical calculations, we assign this intermediate to an excited anion radical that undergoes N1-C1′ glycosidic bond dissociation rather than relaxation to its ground state. Radiation-induced low-energy electrons in solution are implicated in DNA damage, but their relaxation dynamics are not well understood. Here the authors observe how quasi-free electrons dissociate glycosidic bonds via an excited nucleoside anion radical, whereas solvated electrons reside on the nucleoside as a relatively stable anion radical. [ABSTRACT FROM AUTHOR]

Presents a correction to the study "Radiolysis of Liquid Water: An Attempt to Reconcile Monte-Carlo Calculations With New Experimental Hydrated Electron Yield Data at Early Times."