Two types of localized excess electrons in crystalline D2O ice

1977 ◽  
Vol 55 (12) ◽  
pp. 2385-2395 ◽  
Author(s):  
George V. Buxton ◽  
Hugh A. Gillis ◽  
Norman V. Klassen
Keyword(s):  
Absorption Band ◽  
Infrared Absorption ◽  
Low Temperatures ◽  
Total Yield ◽  
Equilibrium Concentration ◽  
Electron Trap ◽  
Decay Kinetics ◽  
Infrared Band ◽  
Visible Absorption ◽  
Perfect Lattice

In a pulse radiolysis study of crystalline D2O ice, an intense infrared absorption band with λmax > 2350 nm has been found at low temperatures, in addition to the well-known visible absorption band of the trapped electron. The infrared band is also attributed to trapped electrons, partly because of its similarity to the electron absorption band found recently in some D2O glasses at low temperatures. The effects of temperature, dose per pulse, accumulated dose, and added NH4F, HF, and ND3 on the yields and decay kinetics of both bands have been investigated. It is concluded that the electron trap giving rise to the visible band is a vacancy which at low temperatures is radiation-produced by a two-step spur process. At temperatures close to the melting point the vacancy-trap probably exists before the radiation pulse at equilibrium concentration. The electron trap which gives rise to the infrared band is thought to be a cavity that occurs naturally in the perfect lattice. For previously unirradiated samples the infrared band decays by a second order process which is remarkably fast [Formula: see text] The decay reaction is probably neutralization by D2O+. Doping with NH4F increases the yield of the infrared absorption and greatly decreases its decay rate. The total yield of localized electrons in irradiated crystalline D2O is higher than has been generally recognized.

Evidence for a second kind of trapped electron in some deuterated aqueous glasses at low temperatures. A pulse radiolysis study

1976 ◽  
Vol 54 (3) ◽  
pp. 367-381 ◽  
Author(s):  
George V. Buxton ◽  
Hugh A. Gillis ◽  
Norman V. Klassen
Keyword(s):  
Absorption Band ◽  
Ethylene Glycol ◽  
Low Temperatures ◽  
High Energy ◽  
No Emission ◽  
Infrared Band ◽  
Visible Absorption ◽  
Trapped Electrons ◽  
Visible Band ◽  
Trapped Electron

Several deuterated aqueous glasses have been pulse-irradiated at 76 K. In addition to the well known visible absorption band of et−, a second intense infrared absorption band, with λmax > 3200 nm, has been found in (a) 50% by volume ethylene glycol, (b) 9.5 M LiCl, and (c) 2.5 and 4 M MgCl2 glasses. Electron scavengers decrease the intensities of both bands, but to different extents. An increase in temperature decreases the intensity of the infrared band, but not that of the visible band. These and other features lead us to conclude that the infrared band is due to shallowly trapped electrons which are distinctly different from trapped electrons which absorb in the visible region.The decay of the infrared band extends over several orders of magnitude in time and, unlike that of the visible band, is independent of wavelength. In the two chloride glasses the decay of the infrared band is accompanied by emission (λmax ≈ 410 nm) and is probably due to a spur reaction between an electron and hydroxyl radical to form excited hydroxide ion. No emission is found in the ethylene glycol glass, but growth of the visible band matches the decay of the infrared band in this case.By comparing the amount of Ag0 produced in an ethylene glycol glass containing Ag+ with the decrease in intensity of the infrared and visible bands, we obtain ε1400 = (5.7 ± 0.8) × 103 M−1 cm−1. From the shape of the infrared band, which is Lorentzian on the high energy side, we estimate λmax ≈ 3600 nm and εmax ≈ 4.9 × 104 M−1 cm−1.

ANALYSIS OF THE PROFILE OF THE FUNDAMENTAL INFRARED BAND OF HYDROGEN IN PRESSURE-INDUCED ABSORPTION

1964 ◽  
Vol 42 (5) ◽  
pp. 873-885 ◽  
Author(s):  
J. L. Hunt ◽  
H. L. Welsh
Keyword(s):  
Absorption Band ◽  
Infrared Absorption ◽  
Line Shape ◽  
Computational Procedure ◽  
Pure Hydrogen ◽  
Square Root ◽  
Infrared Band ◽  
Integrated Intensities ◽  
Boltzmann Law ◽  
Dispersion Line

The pressure-induced fundamental infrared absorption band of hydrogen was measured for a series of pressures in the pure gas and in a H2–He mixture at 300 °K, 195 °K, and 78 °K, and in H2–A and H2–N2 mixtures at 300 °K. The band profiles were separated by a computational procedure into QP and QR (overlap) components and QQ and S(J) (quadrupole) components using a dispersion line shape modified by the Boltzmann law. The dispersion half-width obtained for the overlap components was about twice as great as for the quadrupole components; both half-widths varied as the square root of the temperature. The S(J) lines in pure hydrogen consisted of single and double transitions, the relative intensities of which were in accordance with the assumption of quadrupole interaction. Ortho–para ratios of 3:1 and 1:1 were used in the experiments; the integrated intensities of the band showed very little dependence on the ortho–para ratio, in disagreement with a previously reported result.

A STATISTICAL APPROACH TO THE ANALYSIS OF INFRARED BAND PROFILES

1963 ◽  
Vol 41 (3) ◽  
pp. 750-762 ◽  
Author(s):  
R. Norman Jones ◽  
K. S. Seshadri ◽  
N. B. W. Jonathan ◽  
J. W. Hopkins
Keyword(s):  
Absorption Band ◽  
Time Constant ◽  
Infrared Absorption ◽  
Statistical Approach ◽  
Carbon Disulphide ◽  
Quantitative Description ◽  
Infrared Band ◽  
Kurtosis Parameter ◽  
Cauchy Index ◽  
Absorbance Curve

A method is described for the quantitative description of the profile and asymmetry of an infrared absorption band, based on the computation of the second and third incomplete moments of the absorbance curve. Provision is included for differentiation between the intrinsic band asymmetry and that induced by instrumental factors dependent on the direction of scan. A program has been prepared for an I.B.M. 1620 computer to facilitate the calculation of the moments. This program also yields the incomplete fourth moments, the statistical kurtosis parameter ([Formula: see text]), and the Gauss–Cauchy index, though these quantities are not employed in the present investigation. Examples are given of the application of these computations to the analysis of the effect of the spectral slit width on the profiles of bands at 812.7 and 726.6 cm−1 respectively in the spectra of carbon disulphide solutions of perylene and anthracene, and of the effect of the amplifier time constant on the asymmetry of the band at 2234.4 cm−1 in the spectrum of p-chlorobenzonitrile in tetrachloroethylene solution.

Pressure Narrowing of the Rotational Lines of the Fundamental Infrared Band of H2 in Collision-Induced Absorption

1971 ◽  
Vol 49 (3) ◽  
pp. 381-384 ◽  
Author(s):  
J. De Remigis ◽  
J. W. Mactaggart ◽  
H. L. Welsh
Keyword(s):  
Absorption Band ◽  
Infrared Absorption ◽  
Half Width ◽  
Density Range ◽  
Infrared Band ◽  
Induced Absorption ◽  
Infrared Absorption Band

The enhancement by argon of the pressure-induced fundamental infrared absorption band of hydrogen is studied for Ar densities in the range 8–820 amagat at 152 K. The half-width, Δv1/2, of the quadrupole-induced S1(1) transition remains constant at 55 cm−1 up to ~300 amagat and then decreases to 25 cm−1 at the highest density. In the higher density range Δv1/2 varies inversely as the density. The S1(1) line of H2 in liquid H2–Ar solutions shows a similar pressure narrowing for Ar densities in the range 640–833 amagat at 115 K.

PRESSURE-INDUCED INFRARED ABSORPTION OF GASEOUS HYDROGEN AND DEUTERIUM AT LOW TEMPERATURES: II. ANALYSIS OF THE BAND PROFILES FOR HYDROGEN

1967 ◽  
Vol 45 (9) ◽  
pp. 2859-2871 ◽  
Author(s):  
A. Watanabe ◽  
H. L. Welsh
Keyword(s):  
Infrared Absorption ◽  
Low Temperatures ◽  
Theoretical Calculations ◽  
Computational Procedure ◽  
Gaseous Hydrogen ◽  
Infrared Band ◽  
Line Form ◽  
Dispersion Line ◽  
Good Agreement

Experimental profiles for the pressure-induced fundamental infrared band of hydrogen for a number of temperatures in the range 18–77 °K were analyzed by a computational procedure. Half-widths and peak intensities of 11 components, assumed to have a Boltzmann-modified dispersion line form, were obtained from the analysis. The contributions of the quadrupolar and overlap interactions to the total intensity, as well as their variation with temperature, showed good agreement with theoretical calculations on the exp–4 model.

Octahedral–tetrahedral equilibria in aqueous cobalt(II) solutions at high temperatures

1980 ◽  
Vol 58 (14) ◽  
pp. 1418-1426 ◽  
Author(s):  
Thomas Wilson Swaddle ◽  
Leonard Fabes
Keyword(s):  
Sulfuric Acid ◽  
High Temperature ◽  
Absorption Band ◽  
High Temperatures ◽  
Intensity Ratio ◽  
Hydrogen Sulfate ◽  
Sulfate Ion ◽  
Acidic Media ◽  
Visible Absorption ◽  
Upper Limits

Evidence is presented to indicate that aqueous Co2+ exists as the hexaaquo-ion in equilibrium with minor amounts (upper limits 0.08% at 298 K, 7% at 625 K, at 16–25 MPa) of tetraaquocobalt(II), with ΔH ~ +17 kJ mol−1. The single visible absorption band of the supposed Co(H2O)42+ has maxima at 552 nm and 486 nm in the intensity ratio 2:1. Hydrogen sulfate ion (up to 0.5 M at least) does not complex Co2+(aq) detectably in acidic media, 290–625 K, and sulfuric acid therefore holds promise as a non-complexing strong monobasic acid for high-temperature aqueous studies. In water containing 2.0 M or more Cl−, the tetrahedral form of cobalt(II) is CoCl42−, ΔH for the octahedral → tetrahedral equilibrium being +62 kJ mol−1; forCoBr42−, the corresponding ΔH is +70 kJ mol−1, the greater endothermicity accounting entirely for the lower stability relative to CoCl42−.

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