Search

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]

The radical yields in the aqueous solutions of thiocynate and methyl viologen (MV2+) produced due to radiolysis of water are measured by using proton pulses of 5.2 MeV energy. The amount of yield obtained suggest that the predicted OH radical yields for proton beams in both sets of solution increase with increasing scavenging capacity and approach the value found for high-energy electron radiolysis.

Copyright of Canadian Journal of Chemistry is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A quick measurement system of a continuous absorption spectrum covering a wide range from 200 to 950 nm was constructed by employing an optical multi-channel detector. Ion beam pulse radiolysis with 12.5 MeV/u He, 18.3 MeV/u C and 17.5 MeV/u Ne ions were performed with the measurement system. Transient absorption spectrum of ( S C N ) 2 • − was clearly observed in KSCN aqueous solutions within a few minutes in spite of their very small absorbance, demonstrating high sensitivity of 0.001–0.003 in absorbance in the range from 260 to 660 nm as well as short measurement time of a few minutes. Two different absorption peaks attributed to Br 2 • − and Br 3 − were observed simultaneously in NaBr aqueous solutions, showing powerfulness of the measurement system in overviewing chemical kinetics under ion beam irradiation especially in not well investigated chemical systems. [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]

Predicting the effects of coolant water radiolysis induced by neutron and gamma radiation in the International Thermonuclear Experimental Reactor (ITER) is important, as oxidizing species like O 2 and H 2 O 2 will corrode structural materials, increasing maintenance costs and potentially compromising safety. In this work, a new model has been developed, by modifying existing models, to evaluate the water radiolysis behaviors in different Primary Heat Transfer Systems (PHTSs) in ITER. The new model takes the circulation of coolant, and the combined gamma and 14 MeV neutron radiation into consideration. We recommend injection of about 5 cc H 2 under standard temperature and pressure (STP) per kilogram of H 2 O into the First Wall/Blanket (FW/BLKT) PHTS to both efficiently suppress water radiolysis and avoid problems caused by addition of excessive H 2 . [ABSTRACT FROM AUTHOR]