Wavelength-dependent kinetics

R26 are shown. From Fig. 4, we can see that the dynamics of the initial ET depends on the probing wavelengths. This phenomenon is usually called the wavelength-dependent kinetics. Obviously, the one-step model cannot account for this wavelength-dependent kinetics phenomenon because in this case only one rate constant is involved. In order to understand the origin of wavelength-dependent kinetics, the detailed mechanism of the initial ET in RCs should be constructed. 

The wavelength-dependent data provide spectral information, useful for assignment or structural purposes, while the time-dependent data lead to information relating to the kinetics of the processes that occur in the sample. 

Although exit channel effects are capable of producing a range of non-Boltzmann population distributions, the wavelength dependence of the kinetic energy provides an indication that nonthermal activation is responsible for the fast component of the desorption signal. The activation mechanism responsible for this desorption process is not determined from these experiments, but will be re-addressed in section 4.6. 

We also have found an unexpected detection-wavelength dependence of the observed kinetics at both room and low temperature This observation can be rationalized under the assumption that the kinetics at some wavelengths contain contributions from molecular readjustments (reorganizations) involving the pigments and/or the protein in response to electron transfer ... 

Temperature Dependence of the Kinetics. In an earlier article (22) we gave a detailed analysis of the temperature dependence of the rate of electron transfer from 1 (BPh ) to Q (Figure 4). Here we summarize some of the important considerations and discuss further the possible insights that the temperature and detection-wavelength dependence of the kinetics may give into the molecular mechanism of electron transfer and the overall charge separation process. 

Detection Wavelength Dependence of the Kinetics. The decay time of 100 ps measured at low temperature in the 665-nm anion band appears to be the same as the kinetics of the absorption changes in the 545-and 765-nm ground-state bands of BPh (Table 1). These results are consistent with the view that the BPh that receives an electron has its Ox Qy bs ds at 545 and 765 nm respectively (resolved at low... 

Mitchell, North Carolina, Air Waste, 43, 1074-1083 (1993). Arakaki, T., C. Anastasio, P. G. Shu, and B. C. Faust, Aqueous-Phase Photoproduction of Hydrogen Peroxide in Authentic Cloud Waters Wavelength Dependence, and the Effects of Filtration and Freeze-Thaw Cycles, Atmos. Environ., 29, 1697-1703 (1995). Arakaki, T., and B. C. Faust, Sources, Sinks, and Mechanisms of Hydroxyl Radical ( OH) Photoproduction and Consumption in Authentic Acidic Continental Cloud Waters from Whiteface Mountain, New York The Role of the Fe(r) (r = II, III) Photochemical Cycle, . /. Geophys. Res., 103, 3487-3504 (1998). Atkinson, R., D. L. Baulch, R. A. Cox, R. F. Hampson, Jr., J. A. Kerr, M. J. Rossi, and J. Troe, Evaluated Kinetic and Photochemical... 

The wavelength dependence in Eq. 14.13 can be used for experimental measurements of the surface and kinetic coefficients that constitute Bs. If an array of evenly spaced parallel grooves is introduced on a surface, the spacing dependence of the grooves amplitude-decay factor can be measured [6]. An analysis for flattening of an isotropic surface by bulk diffusion as in Fig. 3.7 is presented in Exercise 14.1. 

Kirmaier, C., Holten, D., and Parson, W. W., 1985a, Temperature and detection-wavelength dependence of the picosecond electron transfer kinetics measured in Rhodopseudomonas sphaeroides reaction centers Resolution of new spectral and kinetic components in the primary charge-separation process. Biochim. Biophys. Acta, 810 33n48. 

Ballard and Van Lienden 16) showed that irradiation of Zr(CH2Ph)4 solutions in the presence of vinyl monomer increased the rate of thermal polymerization by a factor of four. Kinetic rate data suggested that the mechanism of styrene polymerization was wavelength dependent. For... 

To study the influence of the number of chromophores attached to the den-drimer on this second component, the multichromophoric compounds p-C IP3 and P-CIP4 were also studied. As can be seen in Figure 1.19a, the typical shape and wavelength dependence of the partial amplitude is persistent for all three dendrimers, but an additional positive shift can clearly be observed which increases with the number of chromophores. This clearly indicates the contribution of more than one process to this second kinetic component, meaning a more complex attribution compared to the one in the monochromophoric compound. Thus, for the interpretation of these results, two different contributions 2a and 2b to this component are assumed, which are related to different kinetic processes,... 

The rates of reaction of other compounds were also measured relative to this reference compound. Results of such comparisons are presented in Figure 6. Empirical correlations between the kinetic effects of fulvic acid derived peroxy radicals and those of unique reference peroxy radicals indicate that even for this case structure-reactivity relationships can be applied for estimations. However, correlations established for waters containing different types of DOM appear to be somewhat different (Faust and Hoigne, 1987). In addition, because the light screening effects depend on the wavelength, depth functions for different water bodies would require information also on the wavelength dependences of the formation of this environmental factor. 

A topical area of research in chemical kinetics is the detailed study of chemical oscillators.A recent contribution from photochemistry is the study involving the wavelength dependent photoinhibition of oscillations in the reactions of phenol and aniline substrates . ... 

The probe wavelength dependence of the TG signal was measured for a photoinduced electron-transfer system between 9,10-dicyanoanthracene and 1-methylnaphthalene [53]. Owing to its superior sensitivity, the transient absorption spectra could be obtained without using too high of an excitation power. The decay kinetics were analyzed in terms of the back electron transfer to the ground state within 1 1 and 1 2 complexes. 

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