Water lifetime function

Figure 9.35 (a) Fractional amplitudes of the fast (triangles) and slow (circles) modes, and (b) mean lifetimes of the fast (triangles), intermediate (diamonds), and slow (circles) modes of HPC water as functions of polymer concentration. Filled points two-stretched-exponential fits open points three-stretched-exponential fits. The intermediate-mode amplitude has very nearly the same concentration dependence as the fast-mode amplitude. Measurements from O Connell, et al. 70). 

Figure 12.15. Fluorescence lifetime of IR-140 in Aerosol OT (AOT)/iso-octane microemulsions as a function of water pool size to, defined as the molar fraction of water to AOT. (From Ref. 58.)...

Another complication in the quantitation of TIRF on cells is the effect of the membrane thickness itself on the profile of the evanescent wave. Reichert and Truskey<105) have calculated that, in theory, the thickness of the membrane should have a negligible effect on the fluorescence and that a simplified theory of three stratified layers (glass/water/cytoplasm) should be adequate. The theory approximates for simplicity that scattering plays a negligible role and that fluorescence intensity versus angle of observation and fluorescence lifetime are not functions of distance to the interface z. Experiments that... 

Other transient radicals such as (SCN)2 [78], carbonate radical (COj ) [79], Ag and Ag " [80], and benzophenone ketyl and anion radicals [81] have been observed from room temperature to 400°C in supercritical water. The (SCN)2 radical formation in aqueous solution has been widely taken as a standard and useful dosimeter in pulse radiolysis study [82,83], The lifetime of the (SCN)2 radical is longer than 10 psec at room temperature and becomes shorter with increasing temperature. This dosimeter is not useful anymore at elevated temperatures. The absorption spectrum of the (SCN)2 radical again shows a red shift with increasing temperature, but the degree of the shift is not significant as compared with the case of the hydrated electron. It is known that the (SCN) radical is equilibrated with SCN , and precise dynamic equilibration as a function of temperature has been analyzed to reproduce the observation [78],... 

Figure 8.12 shows the projected conversion of S02 to sulfate as a function of the volume of water per cubic meter of air available for conversion in the aqueous phase, covering a range typical of haze particles, fogs, and clouds for atmospheric lifetimes which are typical for each (Lamb et al., 1987). As expected from Eq. (M), the conversion increases with the water available in the atmosphere. As we shall see, the aqueous-phase oxidation does indeed predominate in the atmosphere under many circumstances. Equations (G) and (M) apply as long as the partial pressure of SOz in the gas phase, so,, is measured simultaneously with the solution concentration of S(IV). 

Impurity-related defects (S03 and Cff3) Irradiation of solid C02 doped with water vapour, gaseous S02 and CH4 produces signals of impurity-related defects.124 Contamination of water gave OH radicals with similar g factors but different linewidths. Methyl radicals (CH3 ) and S02 were observed in addition to C02 and C03. H02 radicals generated by electric discharges in C02 atmosphere with moisture were observed in the dry ice frost condensed on the cold tip from the C02 atmosphere. The lifetimes of defects at ambient temperatures of outer planet were obtained by extrapolating the decay time as a function of the absolute reciprocal temperature, 1 /T.m... 

Figure 26. Variation of the fluorescent lifetime of Tb2(S04)3 in a sulfuric acid-water system as a function of water concentration [from Ref. (/0/)J.

The developed model was applied to the EPS experiment (Fig.lb) to extract information on the water dynamics. Similar to the previous report [17], the EPS function decreases rapidly at a time scale of -0.5 ps, then raises again at -2 ps, and finally falls off to zero. The EPS functions acquired while keeping the delays tn (empty circles) and t23 (solid circles) fixed [20], are shifted along the vertical axis which is a consequence of the relatively short excited-state lifetime (700 fs). The peak in the EPS function around -2 ps is explained in the framework of our model as arising from interference between the chromophore and solvent responses. The delicate balance between phases of genuinely nonlinear and thermal contributions as the delay t12 between the two excitation pulses is increased, leads to the enhancement of the integrated signal that is measured in the EPS experiment. 

The lifetime of the hydrogen bonds that the bound water molecules form with the polar headgroups of the surfactant are characterized in terms of two time correlation functions, ShbW and CnB(t), defined as [10],... 

Fig. 3 Hydrogen bond lifetime correlation function for bound water molecules in the CsPFO micellar solution. Inset The same for bulk water. Note the much slower decay of the bound water species.

Thus, Shb(i) decays as soon as the bond breaks for the first time while Chb(1) allows bond breaking at intermediate times. In Fig. 3, we show the water-surfactant hydrogen bond lifetime correlation functions, SnB(t) and ChbM- The decay of SnB(t) for the bound species is much slower than the corresponding decay for the water-water hydrogen bond in pure water [8]. 

Both Ti and T2 relaxations of water protons are mainly due to fluctuating dipole-dipole interactions between intra- and inter-molecular protons [62]. The fluctuating magnetic noise from all the magnetic moments in the sample (these moments are collectively tamed the lattice) includes a specific range of frequency components which depends on the rate of molecular motion. The molecular motion is usually represented by the correlation time, xc, i.e., the average lifetime staying in a certain state. A reciprocal of the correlation time corresponds to the relative frequency (or rate) of the molecular motion. The distribution of the motional frequencies is known as the spectral density function. 

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