Continuity recombination rate

Chance and co-workers have designed a flow system where the protein is continuously pumped optically using a tungsten or xenon flash lamp (764 nm). Using continuous illumination for various times and temperatures. Chance et al. have observed three intermediate states upon MbCO photolysis. At 40 K, a state with a recombination rate constant of 2 x 10 /s has been identified from two slower states with rate constants of 10 /s. 

The first successful RYDMAR experiment on reaction centers was carried out by Bowman et al. [124] using laser flashes and pulsed X-band microwaves of high intensity. Recently, a sensitive RYDMAR technique was developed by Mohl et al. [125] using a combination of continuous illumination with weak magnetic fields (100 to 200 G) and low-intensity microwave radiation at about 300 MHz. Typical spectra are displayed in Fig. 9. From a simulation of these spectra and from their variation with microwave intensity it was concluded that D(P BPh 20 G, 2/(P BPh") = 10.1 0.5 G and the sum of the recombination rates to P, P and... 

The interpretation of measured flame profiles by means of the continuity equations may be approached in one of two ways. The direct experimental approach involves the use of the measured profiles to calculate overall fluxes, reaction rates, and hence rate coefficients. Its successful application depends on the ability to measure the relevant profiles, including concentrations of intermediate products. This is not always possible. In addition, the overall fluxes in the early part of the reaction zone may involve large diffusion contributions, and these depend in turn on the slopes of the measured profiles. Thus accuracy may suffer. The lining up on the distance axis of profiles measured by different methods is also a problem, and, in quantitative terms, factor-of-two accuracy is probably about the best that may normally be expected from this approach at the position of maximum rate. Nevertheless, examination of the concentration dependence of reaction rates in flames may still provide useful preliminary information about the nature of the controlling elementary processes [119—121]. Some problems associated with flame profile measurements and their interpretation have been discussed by Dixon-Lewis and Isles [124]. Radical recombination rates in the immediate post-combustion zones of flames are capable of measurement with somewhat h her precision than above. 

We shall not discuss further the theoretical problems of the validity of equation (1.81) under general conditions. Instead, we shall continue to use this relation to convert calculated dissociation rates into recombination rates. For this, we shall take the statistical expression for the equilibrium constant equ for the reaction... 

Experimental techniques available to investigate sulfoxyl radicals have not changed significantly since the publication of the aforementioned reviews. ESR spectroscopy still remains the most informative and probably the most sensitive detection method. Unfortunately, a low time resolution of continuous wave (CW) ESR spectrometers with 100 kHz field modulation makes them incapable of providing significant kinetic information except for, perhaps, recombination rates. More advanced time resolved ESR techniques still have a limited application in kinetic studies and we are not aware of such techniques having been employed to study the reactions of sulfoxyl radicals. 

Recombination is either characterized using steady state measurements, for instance in the dark or under open-circuit conditions, or transient methods where the decay of the concentration of charges is used to analyze the strength and type of recombination. To determine the recombination rate itself is not useful because the continuity equations are solved in terms of the charge densities of electrons and holes on which the recombination rate is strongly dependent. Therefore, we need to measure directly a recombination lifetime r or an effective recombination prefactor k, which is usually defined as k = R/rP, where n is the average excess electron and hole concentration. Typically, these measurements are done by transient photovoltage measurements [31, 42, 148-152], by transient absorption measurements [148, 153] or by impedance measurements [154—156]. 

By introducing (3.17) into the divergence of (3.16) and simultaneously adding and subtracting net generation-recombination rate we obtain two continuity equations... 

We consider a v-lype magnetoconcentralion detector. The crossed electric and magnetic field cause the depletion of a part of its volume. In an ideal case this would mean that the Auger g-r processes would be sufficiently suppressed to be negligible in comparison to radiative recombination. We further assume that material is sufficiently pure to allow to neglect Shockley-Read processes in bulk. Thus the generation term in the continuity equation reduces to the radiative term. Besides the bulk radiative lifetime we include in it a term of the form US (5 is surface recombination rate which is of SR nature). Then we assume that both of these terms have the identical dependence on the carrier concentration, so that the... 

The following conditions are stipulated the catalyst decomposition rate constant must be one hour or greater the residence time of the continuous reactor must be sufficient to decompose the catalyst to at least 50% of the feed level the catalyst concentration must be greater than or equal to 0.002 x Q, where the residence time, is expressed in hours. An upper limit on the rate of radical formation was also noted that is, when the rate of radical formation is greater than the addition rate of the primary radicals to the monomers, initiation efficiency is reduced by the recombination of primary radicals. 

Rate Constants of Recombination of Alkylsulfonyl Radicals—continued... 

Rate Constants of Recombination and Disproportionation of Aminyl Radicals in Hydrocarbon Solutions Measured by the Flash Photolysis Technique—continued... 

---