Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol

2010 ◽  
Vol 88 (10) ◽  
pp. 1026-1033 ◽  
Author(s):  
Y. Yan ◽  
M. Lin ◽  
Y. Katsumura ◽  
Y. Muroya ◽  
S. Yamashita ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Maximum ◽  
Pulse Radiolysis ◽  
Electron Pulse ◽  
Density Range ◽  
Supercritical State ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Absorption Energy ◽  
Increasing Temperature

The optical absorption spectra of the solvated electron ([Formula: see text]) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220–270 °C. Over the density range studied (~0.45–0.59 g/cm3), the position of the absorption maximum ([Formula: see text]) of [Formula: see text] is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, [Formula: see text] decreases monotonically with increasing temperature in passing through the phase transition at Tc (239.5 °C). By contrast, at a fixed density, [Formula: see text] exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and super-critical regimes. The effect of the addition of a small amount of water to the alcohol on the optical absorption energy of [Formula: see text] is also investigated.

Article

1998 ◽  
Vol 76 (4) ◽  
pp. 411-413
Author(s):  
Yixing Zhao ◽  
Gordon R Freeman
Keyword(s):  
Absorption Spectrum ◽  
Optical Absorption ◽  
Temperature Dependence ◽  
Optical Absorption Spectrum ◽  
Infrared Light ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Tert Butanol ◽  
Solvent Dependence ◽  
Increasing Temperature

The energy and asymmetry of the optical absorption spectrum of solvated electrons, es- , change in a nonlinear fashion on changing the solvent through the series HOH, CH3OH, CH3CH3OH, (CH3)2CHOH, (CH3)3COH. The ultimate, quantum-statistical mechanical, interpretation of solvated electron spectra is needed to describe the solvent dependence. The previously reported optical spectrum of es- in tert-butanol was somewhat inaccurate, due to a small amount of water in the alcohol and to limitations of the infrared light detector. The present note records the remeasured spectrum and its temperature dependence. The value of the energy at the absorption maximum (EAmax) is 155 zJ (0.97 eV) at 299 K and 112 zJ (0.70 eV) at 338 K; the corresponding values of G epsilon max (10-22 m2 aJ-1) are 1.06 and 0.74. These unusually large changes are attributed to the abnormally rapid decrease of dielectric permittivity of tert-butanol with increasing temperature. The band asymmetry at 299 K is Wb/Wr = 1.8.Key words: optical absorption spectrum, solvated electron, solvent effects, tert-butanol, temperature dependence.

Étude par radiolyse pulsée des propriétés spectrales et cinétiques de l'électron solvaté dans l'hexane-1,2,6-triol liquide

1995 ◽  
Vol 73 (1) ◽  
pp. 117-122 ◽  
Author(s):  
J.-P. Jay-Gerin ◽  
J. Chevrel ◽  
C. Ferradini ◽  
E. Ray ◽  
M.H. Klapper ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Optical Absorption ◽  
Linear Accelerator ◽  
Pulse Radiolysis ◽  
Order Reaction ◽  
Kinetic Properties ◽  
Solvated Electron ◽  
Solvent Viscosity ◽  
First Order ◽  
Short Times

The optical absorption spectrum of the solvated electron (es−) in liquid hexane-1,2,6-triol has been measured by nanosecond pulse radiolysis at different temperatures (10–40 °C) to investigate the influence of high solvent viscosity values on the spectral and kinetic properties of es−. The wavelength at the absorption maximum, λmax, is equal to 560 nm, and its variation with temperature, if it exists in the considered zone, is less than the experimental error. At 20 °C and 150 ns, the value of the product [Formula: see text] of the yield of es− and the molar extinction coefficient at λmax is 2.55 × 104 molecule/(M cm 100 eV). In the context of this work, we have compared results obtained with both a linear accelerator and a Febetron, a comparison that has allowed us to evaluate the influence of variations of the dose per pulse and to extend measurements to short times. In the case of experiments performed with the linear accelerator, es− is found to decay at all wavelengths by a first-order reaction (or by a pseudo-first-order reaction) with an activation energy of ~45 kJ mol−1. By contrast, kinetic curves obtained with the Febetron seem to show a competition in which a second-order law is followed at short times. The fact that the shape of the spectra seems to vary as a function of the dose per pulse indicates the possible intervention of another species whose formation is favored by the use of high radiation doses. In other respects, the kinetics of electron solvation does not seem to be controlled by the viscosity of the solvent in our experimental conditions. Keywords: liquid hexane-1,2,6-triol, pulse radiolysis, linear accelerator and Febetron, solvated electron, optical absorption spectrum, kinetic properties, solvent viscosity, dose and temperature effects.

Solvatation des électrons en excès dans les solvants polaires: corrélation entre les valeurs de εmax, W1/2 et EAmax

1990 ◽  
Vol 68 (4) ◽  
pp. 553-557 ◽  
Author(s):  
J.-P. Jay-Gerin ◽  
C. Ferradini
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Extinction Coefficient ◽  
Molar Extinction Coefficient ◽  
Optical Absorption Spectra ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Half Height

On the basis of data found in the literature, it is shown that a correlation exists between the molar extinction coefficient at the maximum optical absorption of the solvated electron (εmax), its width at half height (W1/2), and the energy corresponding to that maximum (EAmax) Keywords: solvated electrons, polar solvants, optical absorption spectra. [Journal translation]

Yield and properties of solvated electrons created by the γ radiolysis of hexamethylphosphorotriamide

1977 ◽  
Vol 55 (11) ◽  
pp. 1832-1835 ◽  
Author(s):  
M. C. Lebas ◽  
J. Sutton ◽  
A. M. Koulkes-Pujo
Keyword(s):  
Pulse Radiolysis ◽  
Total Yield ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Γ Rays

According to various authors, the value of the yield of the solvated electron in the pulse radiolysis of hexamethylphosphorotriamide (HMPT) varies from 1.2 to 2.4 and increases to 4.2 or 3.1 in the presence of NaBr. We exposed this compound to γ rays after purification and saturation with N2O. N2 was formed with a yield G(N2) = 4.4 ± 0.4. After elimination of a certain number of processes which might also lead to N2 formation, it was concluded that this G(N2) corresponds to the total yield of electrons. This value was confirmed by measuring G(Br−) obtained by radiolysis of HMPT with p-bromophenol as a scavenger. The yield of N2 remains constant whenever solutes generally known as good electron scavengers are added (H+, CH3COCH3, NO3−). An interpretation of the results leads to the suggestion of the formation of a dielectron in this medium.

scholarly journals Optical absorption spectra of solvated electrons in 1-butylamine–water mixed solvents

1995 ◽  
Vol 73 (12) ◽  
pp. 2126-2130 ◽  
Author(s):  
Yixing Zhao ◽  
Gordon R. Freeman
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Pure Water ◽  
Mixed Solvents ◽  
Binary Solvents ◽  
Optical Absorption Spectra ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Selective Solvation ◽  
Ideal Mixing

The optical absorption spectra of es− in 1-butylamine–water mixed solvents increase smoothly in energy and intensity as the water content is increased, with the exception of a small decrease in intensity on going from 95 to 100 mol% water. At 298 K the value of Gεmax increases from 1.42 × 10−21 m2/16 aJ (8.6 × 103 es−L/100 eV mol cm) in pure 1-butylamine to 8.3 × 10−21 m2/16 aJ (50 × 103 es−L/100 eV mol cm) in pure water, and the value of EAmax increases from 115 zJ (0.72 eV) to 278 zJ (1.74 eV). In the pure amine, if G(es−) = 0.27, then εmax = 5.3 × 10−21 m2/es− (3200 m2/mol). The solvent composition dependences of Gεmax and EAmax indicate little selective solvation of es− by water; this might be due to relatively "ideal" mixing of water and amine in the binary solvents. The temperature coefficient −dEAmax/dT = 0.43 zJ/K in pure 1-butylamine, 0.47 in pure water, and has a minimum of 0.27 in the 50:50 mixture. Keywords: 1-butylamine–water mixed solvents, optical absorption spectra, solvated electron, temperature dependence.

Primary mechanisms in the radiolysis of amines: pulse and γ-radiolysis of neutral and acidic ethylamine, n-propylamine and ethylenediamine

1979 ◽  
Vol 57 (15) ◽  
pp. 2013-2021 ◽  
Author(s):  
J. A. Delaire ◽  
J. R. Bazouin
Keyword(s):  
Allyl Alcohol ◽  
Molecular Hydrogen ◽  
Pulse Radiolysis ◽  
Solvated Electron ◽  
Infrared Band ◽  
Solvated Electrons ◽  
Upper Limits ◽  
Transient Spectra ◽  
Alkyl Ammonium

The transient spectra in pure ethylamine (EA), n-propylamine (nPA), and ethylenediamine (EDA) show, besides the visible and infrared band associated with the solvated electron, e−s, a small ultraviolet band attributed to oxidizing radicals. Upper limits for the recombination rate constants k of e−s with the acidic cation are 1.5 × 1012 L mol−1 and 3.5 × 1012 L mol−1s−1 in EA and nPA respectively, and k = 2 × 1010 L mol−1 s−1 in EDA. The yield of e−s at 3 ns (G(e−s)3ns = 1.5, 1.2, and 3.1 molecules/100 eV in EA, nPA, and EDA respectively) has been deduced by biphenyl scavenging. The yield of molecular hydrogen after γ-radiolysis G0(H2) = 5.7 and 3.6 in pure nPA and EDA respectively. The effect of solutes, such as biphenyl, alkyl-ammonium chloride, and allyl alcohol, on G(H2) is interpreted in terms of scavenging of e−s and/or H atoms. From the pulse-radiolysis determination of G(e−s), we deduce [Formula: see text] in nPA.Finally, the decay of solvated electrons seems to occur only via recombination with the cation in EA and nPA, but in EDA there is a competition between this reaction and reaction with oxidizing radicals.

The yield and extinction coefficient of the solvated electron in methanol: pulse radiolysis of nitrobenzene and tetranitromethane solutions

1977 ◽  
Vol 55 (11) ◽  
pp. 2030-2043 ◽  
Author(s):  
David W. Johnson ◽  
G. Arthur Salmon
Keyword(s):  
Pulse Radiolysis ◽  
Optical Pulse ◽  
Basic Solution ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Extinction Coefficients ◽  
Hydroxymethyl Radical ◽  
Direct Measurements ◽  
Wide Range ◽  
Basic Solutions

The radical anion [Formula: see text] NB−, which has a strong absorption spectrum from 250–500 nm, is formed by reaction of nitrobenzene with solvated electrons, es−, and hydroxymethyl radical anions, •CO2O−, with k1 = (1.92 ± 0.35) × 1010 M−1 s−1 and k2 = (1.03 ± 0.02) × 1010 M−1 s−1.[Formula: see text]Gελ is constant for NB− over a wide range of nitrobenzene concentrations in basic solution. By assuming that the yields of scavengeable radicals are the same in neutral and basic solutions we obtain ε(NB−)300 nm = (1.66 ± 0.02) × 104 M−1 cm−1. This value is used to evaluate the yield of es− scavengeable by dilute solutions of solutes as G(es−)esc = 1.20 ± 0.03. Extinction coefficients of es−, hydroxymethyl radicals, •CH2OH, and •CO2O− and the oscillator strength of the es− absorption are calculated.The yields of es− determined by previous workers are discussed in terms of dry, damp, geminate, free, spur, and escaped electrons. A model is constructed in terms of damp, spur, and escaped electrons which compares favourably with experimental scavenging results and direct measurements by optical pulse radiolysis.

The pulse radiolysis of decaborane-14 solutions

1976 ◽  
Vol 29 (1) ◽  
pp. 209 ◽  
Author(s):  
BJ Brown ◽  
DF Sangster
Keyword(s):  
Optical Absorption ◽  
Pulse Radiolysis ◽  
Solvated Electron ◽  
Lower Yield ◽  
Polar Solvents ◽  
Aqueous Acid ◽  
Solvent Systems

Results for the pulse radiolysis of B10H14 in selected solvent systems are reported. In polar solvents the solvated electron is rapidly scavenged by B10H14 with k >~ 2x1010 1. mol-1 s-1. In H2O, CH30H and C2H50H a transient optical absorption (G x ε ≈ 104 1. mol-1 cm-1) attributed to boranyl radicals is observed. A lower yield is observed in aqueous acid and hydrocarbon solutions and in the presence of electron scavengers. The results are consistent with an electron scavenging reaction leading to formation of a boranyl radical.

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