A general model for dispersed kinetics in heterogeneous systems

Activation energies of photoinduced unimolecular, bimolecular and termolecular processes on silica gel surfaces

“…The decay of excited 30 state and radical ion species on silica gel is not uncomplicated due to the heterogeneity of the surface and rates rarely conform to simple exponential kinetics. The model described by Albery et al 41 has been used to characterise the data sets, ensuring a comprehensive exploration of the parameter space 35 in order to obtain a global optimum value for the rate parameters 2,3 .…”

Electron transfer reactions in ternary systems on silica gel surfaces: evidence for radical cation diffusion

“…The kinetics of 30 decay of radical ions on silica gel is not straightforward since the surface is heterogeneous in nature and rates rarely conform to simple exponential kinetics. We have used the model described by Albery et al 4,[12][13][14][15]50 to characterise our data sets, ensuring a comprehensive exploration of the 35 parameter space in order to obtain a global optimum value for the rate constants 13,14 .We have previously shown that energy and electron transfer reactions in these systems are dependent upon the rate of diffusion 13,14 , and in the case of azulene as energy acceptor / 40 electron donor, rates of reaction are largely determined by the rate of diffusion of this relatively more mobile species. We have demonstrated also that energetics play a role in determining electron transfer rates, and have shown a Marcustype dependence of rate on the free energy for electron 45 transfer 4,14 .…”

“…The pulse energy 85 was attenuated using solutions of sodium nitrite in water, to ensure that transient reflectance changes were kept below 10%, where the change in reflectance is directly proportional to the concentration of transient species [47][48][49] grating monochromator (Applied Photophysics) and detected with a side-on photomultiplier tube (Hamamatsu R928). Signal capture was by an LT364 Waverunner digitising oscilloscope (LeCroy), interfaced to an IBM-compatible PC.Transient decay data has been analysed using a model 5 which assumes a log Gaussian distribution of rate constants described previously 13,14,50 according to equation 1 10 which was transformed to have finite integrals as described in the appendix of reference 50 . Here C and C 0 are transient concentrations at times t = t and t = 0 after the laser pulse, γ is the width of the distribution and k is the mean rate constant.…”

“…Transient decay data has been analysed using a model 5 which assumes a log Gaussian distribution of rate constants described previously 13,14,50 according to equation 1 …”

“…The kinetics of 30 decay of radical ions on silica gel is not straightforward since the surface is heterogeneous in nature and rates rarely conform to simple exponential kinetics. We have used the model described by Albery et al 4,[12][13][14][15]50 to characterise our data sets, ensuring a comprehensive exploration of the 35 parameter space in order to obtain a global optimum value for the rate constants 13, 14 .…”