Deferred Luminescence in Organic Matrices at Low and Very Low Temperatures

Laser system with a regenerative amplifier for generation of trains of pulses of variable amplitude

“…Such uncertainty is also reflected in the literature related to γ -radiolysis of materials, for example a reciprocal timedependence [8], a power-law decay (see [26] with numerous references therein) and equation (1) with a close to −1 exponent [10] have all been used. For example original data by Kieffer et al [8] initially fitted by a hyperbolic time-dependence of luminescence were re-analysed by Jonscher et al [26,27] considering a power-law decay.…”

“…Such uncertainty is also reflected in the literature related to γ -radiolysis of materials, for example a reciprocal timedependence [8], a power-law decay (see [26] with numerous references therein) and equation (1) with a close to −1 exponent [10] have all been used. For example original data by Kieffer et al [8] initially fitted by a hyperbolic time-dependence of luminescence were re-analysed by Jonscher et al [26,27] considering a power-law decay. Also, a hyperbolic time-dependence of light emitted after irradiation with an incandescent light has been obtained, in several polymers, provided that analyses were performed at times longer that typically 15 s after the irradiation [14,15].…”

“…It has been shown that various treatments, such as UV [4][5][6], γ [7][8][9][10] and x-ray [11][12][13] irradiation, may induce long-lived luminescence in organic or inorganic materials. The luminescence decay has been fitted by various functions which do not significantly differ from each other, at least on the time scale of our experiments which is greater than 1 s: a reciprocal time-dependence [8], a power-law decay with a close to −1 exponent [13][14][15] and an empirical formula revolving around the form I ∝ (1 + αt) −m , where m is close to unity [10][11][12][13][14][15][16].…”

“…UV [4][5][6], γ [8][9][10] and x-ray [11][12][13][14][15][16][17] irradiation have all been reported to cause ionizing excitations leading to slow radiative recombination. There are essentially two kinds of physical process that have been proposed to explain such a behaviour: (i) diffusion models, as originally proposed by Debye and Edwards [4] and subsequently refined by several authors [18][19][20], and (ii) tunnelling models involving either a homogeneous or inhomogeneous distribution of cation-electron separation distances [10,16,[21][22][23].…”

A study of trapped electrons in LiCl/D2O and other aqueous glasses at temperatures down to 2 K by radiolysis, pulse radiolysis, photolysis, and stimulated luminescence

“…An Arhennius plot of the decay rates above 22 K measured at GE = 2.2 x lo4 yields an activation energy of 0.3 kcal/mol (0.01 eV). An activation energy of -0.04 eV was estimated for the temperature dependent decay rate of etbetween 60 K and 77 K in methylcyclohexane glass (20), another system in which infrared absorbing trapped electrons probably decay by tunnelling.…”