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The reactivity of presolvated electrons with CO2 and N2O was studied in the gas pressure range of 1 to 52 bar. To measure this reactivity, a home-made spectroscopic cell with liquid circulation was developed which can work up to 70 bar of gas pressure. The efficiency of presolvated electron scavenging was determined from the decrease of the solvated electron yield after the application of a 5 ps electron pulse. In addition, the reaction rate between these molecules and solvated electrons was directly determined at gas pressures below the gas critical point, which is in agreement with those presented in the literature measured at gas pressures below

Substitution of the thymidine moiety in DNA by C5-subsituted halogenated thymidine analogs causes significant augmentation of radiation damage in living cells. However, the molecular pathway involved in such radiosensitization process has not been clearly elucidated to date in solution at room temperature. So far, low-energy electron (LEEs; 0–20 eV) under vacuum condition and solvated electrons (e(sol)(−)) in solution are shown to produce the σ-type C5-centered pyrimidine base radical through dissociative electron attachment involving carbon-halogen bond breakage. Formation of this σ-type radical and its subsequent reactions are proposed to cause cellular radiosensitization. Here, we report time-resolved measurements at room temperature showing that a radiation-produced quasi-free electron (e(qf)(−)) in solution promptly breaks the C5-halogen bond in halopyrimidines forming the σ-type C5 radical via an excited transient anion radical. These results demonstrate the importance of ultrafast reactions of e(qf)(−) which are extremely important in Chemistry, Physics, and Biology, including tumor radiochemotherapy.

International audience; Imogolite nanotubes are potentially promising co-photocatalysts because they are predicted to have curvature-induced, efficient electron-hole pair separation. This prediction has however not yet been experimentally proven. Here, we investigated the behavior upon irradiation of these inorganic nanotubes as a function of their water content to understand the fate of the generated electrons and holes. Two types of aluminosilicate nanotubes were studied: one was hydrophilic on its external and internal surfaces (IMO-OH) and the other had a hydrophobic internal cavity due to Si-CH$_3$ bonds (IMO-CH$_3$), with the external surface remaining hydrophilic. Picosecond pulse radiolysis experiments demonstrated that the electrons are efficiently driven outward. For imogolite samples with very few external water molecules (around 1% of the total mass), quasi-free electrons were formed. They were able to attach to a water molecule, generating a water radical anion, which ultimately led to dihydrogen. When more external water molecules were present, solvated electrons, precursors of dihydrogen, were formed. In contrast, holes moved towards the internal surface of the tubes. They mainly led to the formation of dihydrogen and of methane in irradiated IMO-CH$_3$. The attachment of the quasi-free electron to water was a very efficient process and accounted for the high dihydrogen production at low relative humidity values. When the water content increased, 2 electron solvation dominated over attachment to water molecules. Electron solvation led to dihydrogen production, albeit to a lesser extent than quasi-free electrons. Our experiments demonstrated the spontaneous curvature-induced charge separation in these inorganic nanotubes, making them very interesting potential co-photocatalysts.

Gold nanoparticles are known to cause a radiosensitizing effect, which is a promising way to improve radiation therapy. However, the radiosensitization mechanism is not yet fully understood. It is currently assumed that gold nanoparticles can influence various physical, chemical, and biological processes. Pulse radiolysis is a powerful tool that can examine one of the proposed effects of gold nanoparticles, such as increased free radical production. In this work, we shed light on the consequence of ionizing radiation interaction with gold nanoparticles by direct measurements of solvated electrons using the pulse radiolysis technique. We found that at a therapeutically relevant gold concentration (&lt, 3 mM atomic gold, &lt, 600 &mu, g &times, cm&minus, 3), the presence of gold nanoparticles in solution does not induce higher primary radicals&rsquo, formation. This result indicates that energy absorption by gold nanoparticles and related effects such as higher ionization of surrounding media and &bull, OH radicals overproduction are not the reason for the radiosensitizing effect reported in the literature.

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.

The ultradivided matter is used for long in various applications, for example in colloids, inks and paints, cosmetics, stained glasses, catalysts, photographic emulsions, ... But the progressive need of nanoparticles for various miniaturized devices and the different approaches for the synthesis have suddenly increased. All of the bottom-up synthesis methods from a diluted precursor to metal nanoparticles imply several steps: a reduction reaction of ionic precursors by electron transfer, inducing the nucleation of atoms then the growth of the seeds into particles, more or less inhibited by stabilizers. The final size, shape, structure and dispersity of the particles strongly depend on the thermodynamics and the kinetics of these steps. The interaction of high energy radiation with the solvent provides, quantitatively and homogeneously distributed in the bulk, strong electron donors (solvated electrons, reducing radicals) which reduce metal ions as precursors into atoms. The radiation chemistry, on one hand in the steady state regime with an accurate knowledge of the yields of all the radiolytic products, and on the other hand in the pulse regime giving access to time-resolved data, constitutes a unique tool to elucidate the detailed mechanisms and to provide the keys of really controlling these processes in view of various applications.

The ultrafast radiolytic behavior of tributyl phosphate, TBP, has been investigated using 7 ps electron pulses with 7 MeV kinetic energy, from which two key species have been observed and characterized: the TBP solvated electron (eTBP–) and the TBP triplet excited state TBP* (3a) or its fragmentation products. The eTBP– exhibits a broad absorption band in the visible and near-infrared (NIR) spectrum, with a maximum beyond our 1500 nm detection limit. Nitromethane was used to scavenge eTBP– to confirm its absorption spectrum and to determine its associated rate coefficient, 1.0 × 1010 M–1 s–1. The electron’s molar extinction coefficients were found by an isosbestic method using biphenyl as a solvated electron scavenger. The time-dependent radiolytic yield of eTBP– was also determined directly from 7 ps to 7 ns and compared with those in water, tetrahydrofuran, and diethyl carbonate. In less than 10 ns, the decay is not due to the reaction with other solvent molecules and is instead predominantly due to the...

The ionizing radiation in aqueous solutions of gold nanoparticles, stabilized by electrostatic non-covalent intermolecular forces and steric interactions, with antimicrobial compounds, are investigated with picosecond pulse radiolysis techniques. Upon pulse radiolysis of an aqueous solution containing very low concentrations of gold nanoparticles with naked surfaces available in water (not obstructed by chemical bonds), a change to Cerenkov spectrum over a large range of wavelengths are observed and pre-solvated electrons are captured by gold nanoparticles exclusively (not by ionic liquid surfactants used to stabilize the nanoparticles). The solvated electrons are also found to decay rapidly compared with the decay kinetics in water. These very fast reactions with electrons in water could provide an enhanced oxidizing zone around gold nanoparticles and this could be the reason for radio sensitizing behavior of gold nanoparticles in radiation therapy.

International audience; The behavior of carbonates is critical for a detailed understanding of aging phenomena in Li-ion batteries. Here we study the first reaction stages of propylene carbonate (PC), a cyclical carbonate, by picosecond pulse radiolysis. An absorption band with a maximum around 1360 nm is observed at 20 ps after the electron pulse and is shifted to 1310 nm after 50 ps. This band presents the features of a solvated electron absorption band, the solvation lasting up to 50 ps. Surprisingly, in this polar solvent, the solvated electron follows an ultrafast decay and disappears with a half time of 360 ps. This is attributed to the formation of a radical anion PC − •. The yield of the solvated electron is low, suggesting that the radical anions are mainly directly produced from presolvated electrons. These results demonstrate that the initial electron transfers mechanisms are strongly different in linear compared with cyclical carbonates. T he commonly used solvents in lithium-ion batteries (LIBs) are a mixture of linear and cyclical carbonates. 1,2 The mixture of solvents is required to get the desired properties of the electrolyte, i.e., a high electrolytic conductivity, a fair chemical and electrochemical stability, etc. The excess electron in the solvent could then play different roles according to the nature of the carbonates. For instance, the anion radical arising from cyclical carbonates is often postulated in electrochemical reactions. 1,2 In this context, the radiolysis approach is a very suitable method to focus on the electron fate and reactivity. We have recently studied the aging mechanisms in a linear carbonate, diethyl carbonate, by pulse and steady-state radiolysis. 3,4 The purpose of the present work is to investigate the short-time behavior of excess electrons in a prototype cyclical carbonate, i.e., propylene carbonate (PC, see the chemical structure in the inset of Figure 1) which is polar with a static dielectric constant around ε s = 66, and a dipolar moment of 4.9 D. The transient optical absorption spectra detected in neat PC after the electron pulse are given in Figure 1. At the shortest delay time after the end of the pulse, a broad absorption band centered at 1360 nm in the near-infrared (NIR) is observed. This band is shifted slightly to the blue and reaches a maximum at 1310 nm at 50 ps, and then disappears rapidly with a half time of 360 ps (Figure 1). In the presence of H + , by means of HClO 4 addition, the decay of the band is still faster (Figure 2); in the presence of perchloric acid at one molar concentration, the band has fully vanished within the electron pulse (Figure 1, dotted line). Note that, even if HClO 4 contains a small amount of water, the reaction of PC with water is extremely slow (k = 7.1 × 10

Picosecond pulse radiolysis measurements have been performed in neutral and highly acidic aqueous solutions containing silver ions at different concentrations. Silver ion reduction is used to understand the ultrafast chemistry of irradiated water and aqueous solutions. The absorption band measured at the end of the 7-ps electron pulses has an intense band with a maximum at 360 nm due to the formation of silver atoms. Kinetics shows that the amount of silver atom formed at the end of the electron pulse in phosphoric acid solutions is greater than that in neutral water. This unexpectedly high yield of silver atom formation cannot be explained solely by the reaction between silver ions and solvated electrons in neutral solutions nor by the reaction with hydrogen atoms in phosphoric acid solutions. To explain the observed ultrafast reduction of silver ions, the presolvated electron, be it free or paired to the hydronium cation, must react very quickly with a silver ion, potentially competing with geminate recombination of the electron and its sibling radical cation.

International audience; Picosecond pulse radiolysis measurements were performed in neat D2O and H2O in order to study the isotopic effect on the time-resolved yield of the hydrated electron and hydroxyl radical. First, the absorption band of the hydrated electron in D2O, e(D2O)(-), is measured between 250 and 1500 nm. The molar absorption coefficient of the solvated electron spectrum in D2O was determined using the isosbestic point method by scavenging the solvated electron using methyl viologen. The amplitude and shape of the absorption spectrum of the hydrated electron in D2O are different from those previously reported in the literature. The maximum of the hydrated electron in the D2O absorption band is ca. 704 nm with a molar absorption coefficient of (22 900 +/- 500) L mol(-1) cm(-1). Based on this extinction coefficient, the radiolytic yield of e(D2O)(-) just after the 7 ps electron pulse was determined to be (4.4 +/- 0.2) x 10(-7) mol J(-1), which coincides with the one for e(H2O)(-) in H2O. The time-dependent radiolytic yield of e(D2O)(-) was determined from a few ps to 8 ns. To determine the OD center dot radical yield, the contribution of the solvated electron and of the transient species produced by the electron pulse in the windows of the fused silica optical cell was taken into account for the analysis of the transient absorption measurements at 260 nm. Therefore, an appropriate experimental methodology is used for measuring low absorbance at two different wavelengths in ps pulse radiolysis. The yield of the OD center dot radical just after the 7 ps electron pulse was found to be (5.0 +/- 0.2) x 10(-7) mol J(-1). In the spurs of ionization, the decay rate of e(D2O)(-) is slower than e(H2O)(-), whereas the decay rate of OD center dot is similar to the one of OH center dot. Here, the established time-dependent yield of the solvated electron and the hydroxyl radical provide the foundation for improving the models used for spur reaction simulations in heavy water mainly for the chemistry of CANDU reactors.

The formation of a H˙ 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.

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-.

Nanoparticles of silver and gold have been produced in THF and PGMEA in one step by using the gamma-irradiation of Ag+ and KAuCl4 solutions, and by stabilization with the polymer PMMA or the ligand NIPAAm. The clusters have been characterized by their plasmon absorption band, high resolution transmission electron microscopy and energy dispersive spectrometry. The mechanism and the radiolytic yields of the metal atom formation in THF or PGMEA are discussed and compared with other solvents. The radiolytic yields of silver or gold nanoparticles are somewhat lower than in water or alcohols, because of the very low dielectric constant and the stronger competition of the metal ion reduction with the geminate recombination between the solvated electron and the parent cation.

Picosecond pulse radiolysis measurements have been performed in several highly concentrated HClO4 and H3PO4 aqueous solutions containing silver ions at different concentrations. Silver ion reduction is used to unravel the ultrafast reduction reactions observed at the end of a 7 ps electron pulse. Solvated electrons and silver atoms are observed by the pulse (electron beam)-probe (supercontinuum light) method. In highly acidic solutions, ultrafast reduction of silver ions is observed, a finding that is not compatible with a reaction between the H(•) atom and silver ions, which is known to be thermally activated. In addition, silver ion reduction is found to be even more efficient in phosphoric acid solution than that in neutral solution. In the acidic solutions investigated here, the species responsible for the reduction of silver atoms is considered to be the precursor of the H(•) atom. This precursor, denoted (e(-), H3O(+)), is a pair constituting an electron (not fully solvated) and H3O(+). Its structure differs from that of the pair of a solvated electron and a hydronium ion (es(-), H3O(+)), which absorbs in the visible region. The (e(-), H3O(+)) pair , called the pre-H(•) atom here, undergoes ultrafast electron transfer and can, like the presolvated electron, reduce silver ions much faster than the H(•) atom. Moreover, it is found that with the same concentration of H3O(+) the reduction reaction is favored in the phosphoric acid solution compared to that in the perchloric acid solution because of the less-efficient electron solvation process. The kinetics show that among the three reducing species, (e(-), H3O(+)), (es(-), H3O(+)), and H(•) atom, the first one is the most efficient.

Highly concentrated potassium carbonate aqueous solutions are studied by picosecond pulse radiolysis with the purpose of exploring the formation processes of carbonate radical CO3(•-). The transient absorption band of solvated electron produced by ionizing is markedly shifted from 715 to 600 nm when the solute concentration of K2CO3 is 5 mol L(-1). This spectral shift is even more important than that observed for the solvated electron in 10 mol L(-1) KOH solutions. The broad absorption band of solvated electron in K2CO3 solutions overlaps with that of carbonate radical CO3(•-) formed at ultrashort time. Nitrate ion is used to scavenge the solvated electron and to observe the contribution of carbonate radical CO3(•-). The analysis of the amplitude and the kinetics of carbonate radical formation in highly concentrated solutions shows that CO3(•-) is formed within the electron pulse (7 ps) by two parallel mechanisms: a direct effect on the solute and the oxidation of the solute by water radical hole H2O(•+). These two mechanisms are followed by an additional one, by reaction between the solute and OH(•) radical especially in lower concentration. The radiolytic yield of each process is discussed.

For the first time, a setup is performed to carry out picosecond time-resolved experiments in supercritical water (SCW) by pulse radiolysis. The kinetics of the decay of the hydrated electron is measured by transient absorption in the near IR on a time-scale ranging from 50 ps to 6 ns. The decay of the hydrated electrons in supercritical conditions shows a fast component at a short time below 500 ps, which is assigned to the reaction of the hydrated electron with the hydronium cation formed by radiolysis. The dependence of the kinetics on the density of SCW is also examined.

With a revisit of the absorption coefficient of the solvated electron in propane-1,2,3-triol, the temperature-dependent behavior of the absorption spectrum of solvated electron was studied from room temperature to 573 K by pulse radiolysis techniques. The change in the absorption spectrum of solvated electron in propane-1,2,3-triol observed by cooling down from a high temperature to 333 K is compared with that occurring during the electron solvation process at 333 K. The effect of the specific molecular structure of propane-1,2,3-triol compared to other alcohols is discussed.

The absorption spectra of the hydrated electron in concentrated LiCl, LiClO 4 , Li 2 SO 4 , MgCl 2 and Mg(ClO 4 ) 2 deuterated water solutions were measured by pulse radiolysis techniques from room temperature to 300 °C at a constant pressure of 25 MPa. With increasing temperature, the absorption band of the solvated electron for all solutions shifts to larger wavelengths. Whatever the temperature, shifts to shorter wavelengths of the absorption spectrum were observed as salt effects. The results on the shape and broadening of the absorption spectrum are discussed.

Using pump–probe transient absorption spectroscopy, we studied the solvation dynamics of the electron in liquid polyalcohols: ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol and propane-1,2,3-triol. Time-resolved absorption spectra ranging from 440 to 720 nm were measured. Our study shows that the excess electron in the diols presents an intense and wide absorption band in the visible and near-IR spectral domain at early time after two-photon ionization of the neat solvent. Then, for the first tens of picoseconds, the electron spectrum shifts toward the blue domain and its bandwidth decreases as the red part of the initial spectrum rapidly drops, while the blue part hardly evolves. In contrast, in the triol, the absorption spectrum of the electron is early situated in the visible range after the pump pulse and then solely evolves in the red part. The Bayesian data analysis of the observed picosecond solvation dynamics with different models is in favor of a heterogeneous continuous relaxation. That is corroborated by the analogy between the change in the absorption band with increasing time or decreasing temperature. That tends to indicate a similar organization disorder of the solvent. Moreover, the electron solvation dynamics is very fast in propane-1,2,3-triol despite its high viscosity and highlight the role of the OH-group in that process.

In neutral and acidic aqueous solutions containing 2 mol L −1 of Cl − , the decay of the solvated electron and the formation of ClOH − and Cl 2 - were studied by picosecond pulse radiolysis experiment. The rate constant for the reaction of e s − and H 3 O + is 1.3 × 10 10 L mol −1 s −1 . The yield of the OH radical at 100 ps is estimated to be 5.0 × 10 −7 mol J −1 .

Using pump-probe transient absorption spectroscopy we studied the solvation dynamics of the electron in liquid polyalcohols: ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol and propane-1,2,3-triol. First, transmission measurements allowed us to assess that electrons were produced via two-photon ionization of the solvent with 263 nm femtosecond laser pulses, and to determine the two-photon absorption coefficient of the polyols. Second, time-resolved absorption spectra ranging from 440 to 710 nm were measured. Our study shows that the excess electron in the diols presents an intense and wide absorption band in the visible and near-IR spectral domain at early time after photoionization. Then, for the first tens of picoseconds the electron spectrum shifts toward the blue domain and its bandwidth decreases as the red part of the initial spectrum drops rapidly while the blue part hardly evolves. Using Bayesian data analysis method, the observed picosecond solvation dynamics were reconstructed with three models: a two-step mechanism and two continuous relaxation models. Comparison between the ability of models to reproduce the experimental kinetics is in favor of a heterogeneous continuous relaxation. Recent results obtained in propane-1,2,3-triol show that the electron solvation dynamics is very fast in this solvent despite its high viscosity and highlight the role of the OH group in that process.

The solvation dynamics of excess electrons in glycerol have been measured by the pump-probe femtosecond laser technique at 333 K. The electrons are produced by two-photon absorption at 263 nm. The change in the induced absorbance is followed up to 450 ps in the spectral range from 440 to 720 nm. The transient signals of electron solvation have been analyzed by two kinetic models: a stepwise mechanism and a continuous relaxation model, using a Bayesian data analysis method. The results are compared with those previously published for ethylene glycol (J. Phys. Chem. A 2006, 110, 175) and for propanediols (J. Phys. Chem. A 2007, 111, 4902). From the comparison, it is pointed out that solvation dynamics in glycerol is very fast despite its high viscosity. This is interpreted as the existence of efficient traps for the electrons in glycerol with low potential energy. The small shift of the absorption band of the excess electron indicates that the potential of these traps is very close to that corresponding to the fully solvated electron.

Picosecond pulse radiolysis measurements of tetrahydrofuran (THF) solutions containing LiClO4 over a wide range of concentration are performed to investigate the formation of transient species. The (35)Cl NMR measurements of these solutions prior to irradiation show that the salt is in the form of (LiClO4)n oligomers. Kinetics and transient absorption spectra of intermediates in each solution are obtained on the time scale from 10 to 3800 ps. A global spectro-kinetic matrix of the data is analyzed by the multicurve resolution alternated least-squares (MCR-ALS) method. It shows the presence of 3 transient species induced by electron pulse, in addition to the solvated electron. A hybrid Monte Carlo/DFT molecular simulation method is elaborated, using the MPW1K functional for the configuration sampling and B3LYP for the spectra calculations. The maximum of the absorption band of the monomer (LiClO4)(-), dimer (LiClO4)2(-), trimer (LiClO4)3(-), and tetramer (LiClO4)4(-) anions are deduced from the simulations. They enable one to label the MCR-ALS spectra (differences are below 0.1 eV) and to interpret the kinetic data. The simulations show also that Li(I) ion catalyzes the reduction of perchlorate by excess electrons. Only the dimer anion, due to its unique structure with a stable Li2(+) core and two nonbridging perchlorates, presents higher stability toward ClO4(-) reduction into ClO3(-). It corresponds to the long-lived species observed in the experiments.

The first reduction steps of iron (II) in 2-propanol have been studied by pulse radiolysis technique. The rate constant value of the reaction of solvated electron with iron (II) was found to be 4.8 × 10 9 dm 3 mol −1 s −1 . The absorption spectrum of Fe(I) with a maximum at 350 nm was determined. The radiolytic reduction of Fe II in 2-propanol under an inert atmosphere leads to the formation of very small iron nanoparticles whereas under a CO atmosphere, the stable Fe(CO) 5 complex is formed.

The absorption spectra of the solvated electron in 1,2-ethanediol (12ED), 1,2-propanediol (12PD), and 1,3-propanediol (13PD) have been determined by nanosecond pulse radiolysis techniques. The maximum of the absorption band located at 570, 565, and 575 nm for these three solvents, respectively. With 4,4'-bipyridine (44Bpy) as a scavenger, the molar extinction coefficients at the absorption maximum of the solvated electron spectrum have been evaluated to be 900, 970, and 1000 mol-1 m2 for 12ED, 12PD, and 13PD, respectively. These values are two-thirds or three-fourths of the value usually reported in the literature. With these extinction coefficients, picosecond pulse radiolysis studies have allowed us to depict the radiolytic yield of the solvated electron in these solvents as a function of time from picosecond to microsecond. The radiolytic yield in these viscous solvents is found to be strongly different from that of water solution.

The present work reports the first pulse-probe absorbance measurements of the hydrated electron at picosecond range and at elevated temperature. The decay of the hydrated electron, from room temperature up to 350 °C, is observed at 790 nm using a laser triggered picosecond electron accelerator. With increasing temperature, the decay of the hydrated electron becomes less and less pronounced. At 350 °C, almost a flat signal from 100 ps to 2.75 ns is observed, suggesting an efficient escape of hydrated electrons from spur reactions.

International audience; We report mixed quantum-classical molecular dynamics simulations of the optical absorption spectrum of the solvated silver atom and electron in liquid water. The simple one electron model is shown to be able to reproduce the strong temperature dependence of the absorption spectra of hydrated electron as well as the much weaker dependence for the silver atom. A qualitative explanation is provided for this experimental fact. When extending these simulations to very low densities corresponding to supercritical conditions the results display a progressive “desolvation” of the hydrated electron. Two other distinct theoretical models lead to results similar to those of the present QCMD simulations.

Using nanosecond pulse radiolysis, the absorption spectra of the solvated electron have been recorded at different temperatures from 295 to 498 K in 1,2-propanediol (12PD) and 1,3-propanediol (13PD). In both solvents, the optical spectra shift to the red with increasing temperature. While the shape of the spectra does not change in 13PD, a widening on the blue side of the absorption band is observed in 12PD by increasing the temperature from 296 to 473 K.

We produced solvated electron in ethylene glycol by two photon ionization of the solvent with a 263 nm femtosecond laser pulse and followed its dynamics by pump–probe transient absorption spectroscopy. For the first time, time resolved absorption spectra ranging from 450 to 725 nm and around 900 nm were measured revealing the rapid formation of a solvated electron’s precursor which absorbs around 450 nm. We also analysed the geminate recombination of the solvated electron.

The formation and decay rate constants of the pairs (M I I , e - s) involving solvated electron and alkaline earth metal cations (M I I = Sr I I , Ca I I ) are determined by pulse radiolysis measurements in tetrahydrofuran (THF). The pairs present a strong reducing character and can reduce biphenyl to biphenylide radical anion. The observed absorption spectra of the pairs are broad and intense, similar to that of (Mg I I , e - s). Compared to the absorption spectrum of solvated electron which is a single band located around 2250 nm, these absorption spectra are shifted to the blue and present two bands. The structure of the pairs is investigated by ab initio calculations, and their absorption bands are studied with an asymptotical method. The observation of two absorption bands for the pairs (M I I , e s -) is rationalized as a perturbation of the solvated electron by neighboring solutes which stabilize differently its s and p states and split the p states. The absorption spectra are compared with those obtained for the pair of solvated electron and alkali metal cations.

The absorption spectra of the solvated electron were recorded at different temperatures at 100 atm in ethylene glycol (EG) using nanosecond pulse radiolysis techniques. With increasing temperature, the wavelength maxima of the absorption spectra of the solvated electron are shifted to the red from 570 nm at room temperature to around 850 nm at 598 K. Contrary to the case of the absorption band of the hydrated electron at different temperatures which does not present any change of the shape, in EG at higher temperature, between 473 and 548 K the absorption band is wider in the blue side than at room temperature.

The reactivity of the pair formed by magnesium perchlorate with solvated electron in THF with aromatic molecules and halogenated hydrocarbons was investigated by pulse radiolysis. The kinetics of electron transfer from the pair to aromatic molecules with reduction potentials covering a 1 V range were recorded. The corresponding rate constants were determined and show that the pair presents a strong reducing character because it can reduce biphenyl which has a low redox potential. Nevertheless, the pair is still a weaker reducing agent than the solvated electron in THF. Moreover, we estimated the rate constants of the reaction between the pair and different types of alkyl halogenides.

The reactivity of a solvated electron with MgII salts in THF is investigated by pulse radiolysis. With magnesium chloride, no reaction is observed, but when magnesium perchlorate is used, the solva...

International audience; The electron transfer from oxide into water is studied in nanoparticle suspensions of various oxides (SiO2, ZnO, Al2O3, Nd2O3, Sm2O3, and Er2O3) by means of pulse and γ radiolysis. The time-resolved and steady-state investigations of the present study demonstrate independently that whatever the band gap and the electron affinity of the oxide, the electron transfer always takes place in these nanometric systems: Irradiation generates hot electrons which have enough energy to cross the semiconductor–liquid interface. Moreover, picosecond measurements evidence that the spectrum of the solvated electron is the same as in water. Lastly, the decay of the solvated electron is similar on the picosecond to nanosecond time scale in water and in these suspensions, but it is clearly different on the nanosecond to microsecond time scale.

We report a femtosecond laser study of the transient absorption of hydrated electrons generated by 266 nm two-photon ionization of liquid water under very high power laser density (up to 1.5 TW/cm2). The two-photon absorption coefficient of liquid water for femtosecond pulses at 266 nm was determined to be β = (1.8 ± 0.4) × 10-11m/W. The quantum yield of formation of the hydrated electron per absorbed photon at 266 nm is determined to be 0.26 ± 0.02. We observed, for the first time, that the decay of the hydrated electron produced under 1.5 TW/cm2 laser pump power density in pure water is not only due to geminate recombination and that the survival probability of the hydrated electron at 1 ns is 0.16 ± 0.02 under those conditions, where an unprecedented local concentration of the hydrated electron of 0.15 M is produced.

In slightly polar solvents, such as ethylenediamine (EDA), diethylether (DEE) and tetrahydrofuran (THF), the reaction of the solvated electron with divalent magnesium has been studied with the pulse radiolysis technique. The rate constant value of the reaction between solvated MgII and solvated electrons is found to be 4.8×10 9 l mol −1 s −1 in EDA and 1.1×10 10 l mol −1 s −1 in DEE and THF. The reduction of the divalent magnesium in DEE and THF leads to the formation of species absorbing around 950 and 985 nm, respectively. The absorption bands are broad and intense. These species are suggested to be either monovalent magnesium ions or solvated electron–ion pairs (MgII,e−s).

Pulse radiolysis is used to determine the absorption spectra of the transient species formed during the decay of the hydrated electron in an aqueous solution containing AgCl43-. The mechanisms of AgCl43- reduction by solvated electrons and hydroxyalkyl radicals of 2-propanol are discussed. The redox potential of the couples AgCl43-/Ag0Cl44- and AgCl43-/Ag0 + 4Cl- is evaluated. It is shown that the redox potential of the solvated silver atom couple is lowered by the presence of Cl- ligands. The value of the E°(AgCl43-/Ag0Cl44-) is estimated to be around −2.3 VNHE.

The diethyl carbonate, DEC, is an ester that is used as a solvent in Li-ion batteries, but its behavior under ionizing radiation was unknown. The transient optical absorption spectra, the decay kinetics, and the influence of various scavengers have been studied by using the picosecond laser-triggered electron accelerator ELYSE. In neat DEC, the intense near-IR (NIR) absorption spectrum is assigned to the solvated electron. It is overlapped in the visible range by another transient but longer-lived and less intense band that is assigned to the oxidized radical DEC(−H). The solvated electron molar absorption coefficients and radiolytic yield evolution from 25 ps, the geminate recombination kinetics, and the rate constants of electron transfer reactions to scavengers are determined. The radiolytic mechanism, indicating a certain radioresistance of DEC, is compared with that for other solvents.

The formation of the well-known product Br3(-), observed in the steady-state radiolysis of highly concentrated Br(-) aqueous solutions, has now been directly observed at ultrashort times corresponding to the relaxation of the spur. The transient absorption induced by picosecond pulse radiolysis of 6 M Br(-) aqueous solution was probed simultaneously at 260 nm with the third harmonic laser wave and from 350 to 750 nm with a supercontinuum generated by the fundamental laser wave. This approach allows several transient radiolytic species to be followed in parallel, particularly the solvated electron, BrOH(-•), Br2(-•), and Br3(-). The kinetics measured within 4 ns at 260 and 370 nm clearly exhibit that the decay of Br2(•-) is correlated with the formation of Br3(-). In highly concentrated Br(-) solutions, the OH(•) radical is fully replaced by Br2(•-), and the spur kinetics of OH(•) radical in pure water is comparable with that of Br2(-•). Model calculations indicate that the main OH(•) radical combination product H2O2 in pure water has formation kinetics similar to that of Br3(-) in 6 M Br(-) solutions. Moreover, they point out that oxidation of Br(-) occurs within the electron pulse both by direct energy absorption and by scavenging of the water radical cation, H2O(•+).

Pulse radiolysis is used to determine the absorption spectra of the transient species formed during the decay of the hydrated electron in an aqueous solution of AgI1(NH3)2+. The absorption spectrum attributed to Ag01(NH3)2 presents three peaks at 345, 385, and 435 nm. A theoretical estimation of the redox potential of the couple AgI1(NH3)2+/Ag01(NH3)2 yields the value −2.4 VNHE. This value is consistent with the fact that AgI1(NH3)2+ is not directly reduced by (CH3)2ĊO- and shows that the redox potential of the silver monomer couple is lowered by ammonia ligands.

The decay of solvated electron e(s)(-) is observed by nanosecond and picosecond pulsed radiolysis, in diluted and highly concentrated solutions of dichloromethane, CH(2)Cl(2), trichloromethane, CHCl(3), tribromomethane, CHBr(3), acetone, CH(3)COCH(3), and nitromethane, CH(3)NO(2), prepared in ethylene glycol. First, second-order rate constants for the reactions between e(-)(s) and the organic scavengers have been determined. The ratio between the highest rate constant that was found for CH(3)NO(2) and the lowest one that was found for acetone is 3. This difference in reactivity cannot be explained by the change of viscosity or the size of the molecules. Then, from the analysis of decay kinetics obtained using ultrafast pulse-probe method, the distance dependent first-order rate constant of electron transfer for each scavenger has been determined. The amplitude of the transient effect observed on the picosecond time scale differs strongly between these solvated electron scavengers. For an identical scavenger concentration, the transient effect lasts ≈650 ps for CH(3)NO(2) compared to ~200 ps for acetone. For acetone, the distance dependent first-order rate constant of electron transfer is decreasing very rapidly with increasing distance, whereas for nitromethane and tribromomethane the rate constant is decreasing gradually with the distance and its value remains non-negligible even at ~10 Å. This rate constant is controlled mostly by the free energy of the reaction. For nitromethane and tribromomethane, the driving force is great, and the reaction can occur even at long distance, whereas for acetone the driving force is small and the reaction occurs almost at the contact distance. For nitromethane and acetone, the one-electron reduction reaction needs less internal reorganization energy than for alkyl halide compounds for which the reaction occurs in concert with bond breaking and geometric adjustment.

Picosecond pulse radiolysis measurements using a pulse-probe method are performed to measure directly the time-dependent radiolytic yield of the OH(•) radical in pure water. The time-dependent absorbance of OH(•) radical at 263 nm is deduced from the observed signal by subtracting the contribution of the hydrated electron and that of the irradiated empty fused silica cell which presents also a transient absoption. The time-dependent radiolytic yield of OH(•) is obtained by assuming the yield of the hydrated electron at 20 ps equal to 4.2 × 10(-7) mol J(-1) and by assuming the values of the extinction coefficients of e(aq)(-) and OH(•) at 782 nm (ε(λ=782 nm) = 17025 M(-1) cm(-1)) and at 263 nm (ε(λ=263 nm) = 460 M(-1) cm(-1)), respectively. The value of the yield of OH(•) radical at 10 ps is found to be (4.80 ± 0.12) × 10(-7) mol J(-1).

The decay of the solvated electron generated by picosecond electron pulse radiolysis is studied by broad-band transient absorption measurements in ethylene glycol solutions containing decimolar concentrations of Cu2+, Ni2+, and Pb2+ metal cations. Analysis of the nonexponential kinetics of the decays reveals molecular parameters of the electron transfer reaction. It is found that the reaction occurs at long distance for Cu2+ solutions and is only limited to contact distance in the case of Ni2+ solutions. The distribution of reaction distance strongly depends on the free enthalpy change of the reactions.

The decay of the solvated electron generated by picosecond electron radiolysis is measured for highly concentrated oxidizers in a viscous solvent. Analyzing the non-exponential kinetics reveals molecular parameters of the reaction, particularly its distance distribution.

The molar extinction coefficients at the absorption maximum of the solvated electron spectrum have been evaluated to be 900, 970, and 1000 mol−1·m2 for 1,2-ethanediol (12ED), 1,2-propanediol (12PD), and 1,3-propanediol (13PD), respectively. These values are two-third or three-fourth of the value usually reported in the published report. Picosecond pulse radiolysis studies have aided in depicting the radiolytic yield of the solvated electron in these solvents as a function of time from picosecond to microsecond. The radiolytic yield in these viscous solvents is found to be strongly different from that of the water solution. The temperature dependent absorption spectra of the solvated electron in 12ED, 12PD, and 13PD have been also investigated. In all the three solvents, the optical spectra shift to the red with increasing temperature. While the shape of the spectra does not change in 13PD, a widening on the blue side of the absorption band is observed in 12ED and 12PD at elevated temperatures.

Picosecond pulse radiolysis of neat tetrahydrofuran (THF) shows a fast decay of the solvated electron within 2.5ns. The decay of the solvated electron observed at 790nm is because of spur reaction. A numerical simulation using time dependent Smoluchowski equation containing a sink term with a distance dependent reaction rate is used to fit the pulse-probe data and shows that the geminate reaction can proceed at long distance in this low polar solvent.

A selective formation of copper clusters in zeolite nanoparticles with GIS type structure is demonstrated. The size and the shape of the metal clusters are depending on the amount of copper incorporated in the small pores of the GIS crystalline structure and on their aperture. Different kinetics of reduction of the metal cations to clusters is observed under controlled radiolytic treatment of suspensions with constrained nanosized GIS particles. The solvated electrons produced in the bulk water under gamma radiolysis migrate into the GIS nanocrystals and subsequently reduce CuII to CuI starting from the external surface layers and progressing towards the center of the particles; this results in the coexistence of both CuII cations and Cu0 atoms. In the samples with low copper content, the formation of CuI species is not observed, which is associated with the confinement of copper into the small zeolite pores preventing the reaction between Cu2+ and Cun0. The copper loading of the nanocrystals, the conditions of radiolytic treatment and the features of the framework type crystalline structure determine the development of the reduction process resulting in selective formation of CuI or Cu0 species in the GIS nanocrystals.