Recombination rates, measurement

The dissociation rates can now be reconciled fairly well with recombination rates measured in flames at 1000-2000 K. The high collision efficiency of H2O itself as collision partner M, fc(H20)/k(Ar)... 

As outlined at the beginning of this chapter, combined photocurrent and microwave conductivity measurements supply the information needed to determine three relevant potential-dependent quantities the surface concentration of excess minority carriers (Aps), the interfacial recombination rate (sr), and the interfacial charge-transfer rate ( r). By inserting the... 

Another situation in which an already well-studied proton transfer reaction serves as a probe of a physical phenomenon has been suggested by Knight, Goodall and Greenhow (43, 44). They ionized water with single photons of Nd glass laser infrared radiation and measured an ion recombination rate constant for the reaction... 

Here Tio denotes the critical electric field strength expressed in units of V/m, at which the electron mobility deviates 10% from the thermal mobility, and is used as a measure of the rate of the electron energy dissipation in a particular system. Despite its simplicity, Eq. (40) is shown to give reasonable estimates of the electron-ion recombination rate constant for some of the experimentally studied high-mobility systems. 

The measured H atom G-value is about 0.25 at MZ jE = 1, while the equivalent yield of hydrated electrons is found at MZ jE = 10. The persistence of the hydrated electron to higher MZ jE values suggests that it does not decrease to zero at an infinite value of MZ jE. Most H atoms are produced in conjunction with OH radicals in the core of the heavy ion track. The recombination rate constant is high so there is a small probability that H atoms will escape the track at high LET (MZ jE). H atoms can be formed by hydrated electron reactions and their yield cannot decrease to zero if hydrated electron yields do not. However, hydrated electron yields are low at high MZ /E values so the H atom yield can be considered negligible in this region. 

I.R. Hurle, "Measurements of Hydrogen-Atom Recombination Rates Behind Shock Waves , llthSympCombstn (1967), 827-36... 

Returning to the survival probability, in Fig. 57, the kinetic theory and diffusion equation [cf. eqn. (132)] predictions are compared. Three values of the activation rate coefficient are used, being 0.5, 1.0 and 2.0 times the Smoluehowski rate coefficient for a purely diffusion-limited homogeneous reaction, 4ttoabD. With a diffusion coefficient of 5x 10 9 m2 s1 and encounter distance of 0.5 nm, significant differences are noted between the kinetic theory and diffusion equation approaches [286]. In all cases, the diffusion equation leads to a faster rate of reaction. In their measurements of the recombination rate of iodine atoms in hydrocarbon solvents, Langhoff et al. [293] have noted that the diffusion equation analysis consistently predicts a faster rate of iodine atom recombination than is actually measured. Thus there is already some experimental support for the value of the kinetic theory approach compared with the diffusion equation analysis. Further developments cannot fail to be exciting. 

For a process like electron-ion recombination, the presence of resonances closely above the ionization threshold has a large impact on the recombination rate. A number of storage ring measurements, which can map out the resonances in great detail, have clearly shown that one cannot dismiss such resonances just because they would not be able to ionize in LS-coupling. 

Possible applications of laser enhanced ionization in flame diagnostics are 1. simultaneous observation of ionization and fluorescence signals from various levels might provide more information on the sequence of processes leading to and from the ionization continuum 2. the measurement of ion mobilities, relating to cross-sections for elastic collisions between ions and flame particles 3. measurement of ionization rate constants relating to cross-sections for inelastic collisions between excited atoms and other flame particles 4. measurement of recombination rate constants, relating to cross-sections for inelastic collisions between ions, electrons and neutrals. 

More recently, a RuPc bearing a carboxylic moiety in its axial position was also tested for DSSC applications [281]. Transient absorption and steady-state (absorption and emission) measurements revealed that for such a system the electron injection occurs from the RuPc triplet state into the Ti02 conduction band. A detailed study on the variation of the recombination rate constants for a series of metal complexes and organic dyes, including some RuPcs, has been carried out in order to identify some important parameters that should be taken into account for the implementation of DSSCs [282],... 

The ion-electron dissociative recombination-rate constant of reaction (42) has been measured 9 and was found to be approximately 4 X 10 7 ion-1 cc. sec."1. 

An analysis of the time dependent transient photo-reflectance gives us a good estimate of the effective pair recombination rate [8], The inset in Fig. 1(b) shows the average reflectance change as a function of the delay between pump and probe pulses at 6 K. In accordance with other BCS superconductors the effective recombination time is found to be a few nanoseconds. One important remark is that, within the experimental time resolution, no evidence of multiple decays is found. In fact, ultra-fast pump-probe measurements on MgB2 [12, 13] did not find any evidence for a double relaxation down to the ps regime. 

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