Bio: Iwona Szamrej is an academic researcher. The author has contributed to research in topics: Radiolysis & Electron capture. The author has an hindex of 4, co-authored 9 publications receiving 83 citations.
TL;DR: In this paper, the electron capture reaction in the gamma radiolysis of gaseous hydrogen sulphide has been investigated with methyl bromide and hydrogen chloride as the electron scavengers.
Abstract: The mechanism of the electron capture reactions in the gamma radiolysis of gaseous hydrogen sulphide has been investigated with methyl bromide and hydrogen chloride as the electron scavengers. The yields of methane and hydrogen were measured gas-chromatographically. The measurements were performed at two dose rates and in the presence of butadiene as a sulphur scavenger. G(CH4)-1 and ΔG(H2)−1 are a linear function of l/[CH3Br] and 1/[HC1], respectively, and do not depend on the H2S pressure. Lowering the steady-state concentration of product sulphur by approximately 10 times (using a lower dose rate or butadiene) increases the rate of CH4 or H2 production by only approximately 2 times. A mechanism including formation of dimer negative ions of the type (H2S X)−, where X is H2S, SNn, HCl or CH3Br, is proposed
TL;DR: It is shown that dissociative electron attachment is the operative mechanism for the sulfur content amino-acid fragmentation, and the present interest of methionine arises from the implication of the molecule in biological processes.
Abstract: In this work, we present the results from low energy (<12 eV) electron impact on isolated methionine, Met. We show that dissociative electron attachment is the operative mechanism for the sulfur content amino-acid fragmentation. The two most dominant fragments are attributed to the (Met-H)− and (C4NOH5)− ions that are formed at energy below 2 eV. The formation of the latter anion is accompanied by the loss of neutral counterparts, which are most likely a water molecule and highly toxic methanethiol, CH3SH. Further fragments are associated with the damage at the sulfur end of the amino acid, producing the methyl sulfide anion CH3S− or sulfur containing neutrals. In the context of radiation induced damage to biological material at the nano-scale level, the present interest of methionine arises from the implication of the molecule in biological processes (e.g., S-adenosyl methionine for the stimulation of DNA methyltransferase reactions or protein synthesis).
TL;DR: In this article, the Pulsed Townsend technique was used to measure the thermal electron attachment rate for CH 2 ClCHClCH 2 Cl, CH 2 CLCHClCh 2 Cl and CF 2 ClCFCl 2 over the temperature range T ǫ =298-358 K. The corresponding rate coefficients at 298-K are equal to 1.7(4) −1 −10 −10, 7.9(15) −10, 3.4(5) −8 Â cm 3 Âmolec.
TL;DR: In this paper, a mechanism for the observed decrease in the sulfur and hydrogen yields has been discussed, which is attributed to a competition between butadiene and hydrogen sulfide in an excitation transfer from the rare gas metastables and hydrogen atom scavenging.
Abstract: Hydrogen and sulfur yields have been measured from the argon, krypton, and xenon sensitized radiolysis of hydrogen sulfide in the presence of butadiene. A sharp decrease in the yield of elemental sulfur from 5-7 molecules/100 eV down to a very low value (ca. 0.1 atoms/100 eV) has been discovered even at the lowest added amounts of butadiene. Unlike the sulfur yields, the hydrogen yields diminished smoothly with (C/sub 4/H/sub 6/)/(H/sub 2/S) ratio. A mechanism for the observed decrease in the sulfur and hydrogen yield has been discussed. It has been shown that elemental sulfur is produced via the HS/sup +/ ions and SH radicals and/or S atoms as intermediate products, each of them being scavenged by butadiene. The change in G(H/sub 2/) with the (C/sub 4/H/sub 6/)/(H/sub 2/S) ratio was ascribed to a competition between butadiene and hydrogen sulfide in an excitation transfer from the rare gas metastables, and hydrogen atom scavenging. The rate constant ratio k/sub H+H/sub 2/S//k/sub H+C/sub 4/H/sub 6// has been calculated to be in the range of 0.22-0.28, 0.18-0.22, and 0.14-0.16 for Kr, Xe, and Ar, respectively. The observed increase in the rate constant ratio as compared to that for thermal H atoms (0.11) has beenmore » accounted for by a higher kinetic energy of hydrogen atoms produced in the system. The maximum values of G/sub Xe*/, G/sub Kr*/, and G/sub Ar*/ have been found from energetic calculations to be equal to 3.1, 2.5, and 2.1, respectively. These have been compared with experimental results found under the supposition that primary radiolysis can be neglected. The discrepancy has been observed which has been ascribed to the significant decomposition of hydrogen sulfide by electrons subexcited with respect to rare gas atoms. The hydrogen yield due to the last process has been estimated to be ca. 1.4 for Ar and Xe.« less
TL;DR: In this paper, the rate constants of the charge and excitation transfer have been estimated: k/sub Ar/sup +/ + H/sub 2/S/ = 1.8 x 10/sup -9/ cm/sup 3/ s/sup-1/1/
Abstract: Hydrogen and sulfur yields have been determined in the rare gas sensitized radiolysis of hydrogen sulfide. A decrease in G(H/sub 2/) and G(S) has been discovered in each of the three mixtures examined: H/sub 2/S--Ar, H/sub 2/S--Kr, and H/sub 2/S--Xe. A mechanism has been proposed including (1) competition between a charge transfer to H/sub 2/S and Ar/sub 2//sup +/ formation in the H/sub 2/S--Ar system, and (2) competition between an excitation transfer to H/sub 2/S and formation of excited rare gas molecules in H/sub 2/S--Xe and H/sub 2/S--Kr mixtures. Rate constants of the charge and excitation transfer have been estimated: k/sub Ar/sup +/ + H/sub 2/S/ = 1.8 x 10/sup -9/ cm/sup 3/ s/sup -1/, k/sub Kr* + H/sub 2/S/ = (0.6-1.5) x 10/sup -9/ cm/sup 3/ s/sup -1/, and k/sub Xe* + H/sub 2/S/ = 2.7 x 10/sup -9/ cm/sup 3/ s/sup -1/. The relevance of Franck--Condon transitions in the charge-transfer processes has been shown. The maximum recombination energy values of the rare gas molecular ions were estimated as 14.0, 12.7, and 10.8 eV for Ar/sub 2//sup +/, Kr/sub 2//sup +/, and Xe/sub 2//sup +/, respectively.
TL;DR: In this article, the kinematic equations giving the velocity and acceleration of a ball in a vial in a planetary ball mill are given, the kinetic energy transferred at the collision event, the shock frequency, and the injected shock power are also calculated.
Abstract: Based on a kinematic modeling of the planetary ball mill, the kinematic equations giving the velocity and the acceleration of a ball in a vial in a planetary ball mill are given. The kinetic energy transferred at the collision event, the shock frequency, and the injected shock power are also calculated. The confrontation of the calculated to some experimental results documented in the material literature, show that neither the shock energy nor the shock frequency separately taken into account, govern the end product but only the injected shock power is responsible for the ball milled end product.
TL;DR: In this article, the effects of thermal treatment and neutron irradiation on precipitates in Zircaloy have been investigated by analytical electron microscopy, and the process leading to amorphization is discussed based on the effect of irradiation-induced point defects.
TL;DR: Based on a deeper mathematical treatment of the process taking place in a planetary ball mill and experimental results concerning the ball-milled end product of the Ni 10 Zr 7 compound, Wang et al. as discussed by the authors proved that neither the shock frequency nor the shock energy separately governs the ball milled end products as assumed previously.
TL;DR: In this paper, a review of the field of irradiation-induced amorphization of intermetallic compounds is presented, including an update of recent experimental results using in-situ particle irradiation showing the effects of dose rate, temperature, crystal orientation, electron energy and the presence of stacking faults.
TL;DR: In this article, the relationship between electron irradiation induced chemical disordering and the crystalline to amorphous (C-A) transition is studied in the line compound Cu4Ti3.