Jerzy Kroh

Photodissociation of carbon monoxy myoglobin: Kinetics of carbon monoxide rebinding

Abstract Carbon monoxide rebinding following laser photodissociation of carbon monoxy myoglobin in frozen solutions can be adequately described using the second-order equal concentration kinetic equation with a time-dependent rate constant deducible from the Kohlrausch relaxation function.

Electrons trapped in ethanol-water glasses at ultra-low temperatures

Abstract The trapping of electrons in ethanol-water glasses has been studied by pulse radiolysis at temperatures from 6 to 76 K and by γ-radiolysis from 4.2 to 80 K. Addition of water, or increase in temperature, causes the visible absorption band of the spectrum of trapped electrons to increase relative to the IR band. Closer examination of these bands showed that they behave independently in the temperature range 4.2–50 K. It is concluded that both temperature and water content influence the distribution of electrons between pre-existing traps. The distribution of trap depths is non-random and comprises two sets, i.e. shallow (hydrocarbon) and deep (hydroxyl). G ϵ values measured in γ-radiolysis experiments at 4.2 K are much lower than those measured by pulse radiolysis at 6 K. This difference is probably caused by slow charge recombination by tunnelling which involves e - t mainly from the shallow traps.

Trapped electron in frozen ionic solutions— a theoretical model

The theoretical model of electron trapped in frozen solutions of ionic compounds is presented. The model is based on the lattice theory of concentrated electrolytes; water plays the role of dielectric continuum. Two possible ionic structures being the source of attractive potential—cation and anion vacancy—are considered. It appears that due to repulsive effects of the nearest neighbouring anions the cation site is very shallow electron trap or even has no bonding electron level. This structure is presumably responsible for IR absorption bands observed for LiCl or MgCl2 solutions. The F-centre like structure is rather deep trap characterized by electron energy level ca. -3 eV and optical transition ca. 2 eV. The numerical calculations were performed for Li+, Na+ and K+ solutions. The properties of e-vis and e-IR bands are discussed with respect to their explanation by the model.

Decay kinetics of hydroxyl radicals in frozen aqueous systems

Abstract Second- and first-order kinetic equations, respectively, with time-dependent rate constant of the form k(t) = Bt α-1 , 0 , were found to be adequate to describe the decay of OH radicals at temperatures below and above the onset of structural relaxation, at about 100 K, in the frozen aqueous systems (polycrystalline ice and amorphous water imbedded in frozen cross-linked dextran) γ-irradiated at 77 K.

Radioluminescence kinetics of frozen solutions of LiCl

Abstract Isothermal luminescence (ITL) of γ-irradiated frozen solutions of LiCl follows the first-order rate equation with a time-dependent rate constant of the form k(t) = Btα-1, where B and 0

EXCITED STATE FORMATION IN PULSE IRRADIATED POLYETHYLENE DOPED WITH AROMATICS

Abstract The absorption/emission spectra and kinetics of excited states (singlets and triplets) and ions generated by pulse radiolysis method in the polyethylene-solute (dimethyldiphenyl, pyrene) systems were investigated. It was found that excited states of aromatic admixtures were formed as a result of ion recombination in micro/millisecond time scales at temperatures higher than T g . Solute excimer emission was observed from pulse-irradiated PE samples at room temperature. The mechanism of excimer formation was discussed.

Photostimulated decay of trapped electrons in alkaline ice. Pseudo first-order kinetics with time-dependent rate constant

Abstract Photostimulated decay of trapped electrons in alkaline ice can be described by pseudo first-order kinetics with a time-dependent scavenging rate constant of the form k eff ( t ) = B′t α-1 , depending on the light intensity and the concentration of scavenger added

Preexisting traps for electrons in polar liquids. Statistical distributions of trap energy and structure

The statistical distributions of the electron energy level and the structural parameters of the preexisting traps in polar liquids have been investigated. The Monte Carlo calculations were performed for the TIPS intermolecular potentials with the parameters corresponding to the simple alcohols, methanol and ethanol, in liquid phase. The distributions of the trapping level obtained for the TIPS potential seem to be better correlated with the data provided by experiments than the distributions obtained for the point–dipole model of alcohol molecules.

Effect of irradiation temperature on the decay rate of trapped hydrogen atoms in sulfuric acid glasses

Abstract Hydrogen atoms trapped in the glass irradiated at temperature higher than that of observation are more stable, and hydrogen atoms trapped in the glass irradiated at temperature lower than that of observation are less stable than those formed at the temperature of observation. This effect could be described quantitatively with the use of the time-dependent rate constant of form given by equation (1) and (4) with the characteristic time τ 0 given by equation (13).

Pulse radiolysis of solid polyethylene in the presence of pyrene

Abstract A pulse radiolysis study of polyethylene, pure and in the presence of pyrene has been carried out in the temperature range 30–295 K. An absorption band extended up to 2100 nm observed at T Tg and