Singlet recombination probability

The experimentally obtained values show larger divergence based on alkane fluorescence measurement. Walter et al. [148] and Luthjens et al. [65,128] published 0.8-0.9. Later the latter authors modified their value to 0.65 [149]. In solutions of isooctane, cyclohexane, or -hexane with naphthalene, Sauer and Jonah established this value as 0.5 0.1 this singlet formation probability is approximately constant during the decay of charged species up to 70 nsec [150]. In final product experiments/ = 0.34 [151], 0.53, and 0.47 [84] was estimated for cyclohexane, cix-decalin, and trans-6eca m, respectively. The low value for cyclohexane is due to the ionic reactions before recombination. 

Other probes of the initial distribution have been tried. A few studies of the time-dependent ion-pair recombination probability have been made recently with picosecond pulse radiolysis equipment. A magnetic field alters the rate of interconversion between a triplet and singlet ion-pair. If this rate is fast enough to compete with the recombination rate of ions, the yield of recombined ion-pairs is markedly affected by the magnetic field. 

In the encounter RP, the ratio of singlet and triplet spin state populations is 1 3 as shown by reaction (9-12c). The MIE arises almost completely from the T-S conversion of tripler RP. Thus, the recombination probability of peroxy radicals with terminal atoms is higher than that of radicals with terminal 0 or 0 atoms. In the case of polypropylene, the a value of 1.060 0.005 was obtained for O, but 1.015 0.010 for 0. This result certified that (MIE) a(CIE) for reaction (9-12). 

A recent study has provided the needed information [108]. Product yields from the Si state of cis- and trans- decalins were determined in 7.6 eV photolysis. Only 40-50% of these states were found to fragment (which is an unusually low dissociation yield for a saturated hydrocarbon). The yields of the solvent Si states in 3 MeV 3-radiolysis were determined and, combined with the photolysis results, were used to estimate the fraction of radiolytic products that originate from the Si states. The rest of the products were assigned to the Ti states. Table 1 summarizes the results. As seen from this table, for cis- and trans-decalins the probabilities fs of singlet recombination are close to 0.5. This probability is in fair agreement with the recently corrected estimate of f ... 

Theory shows that in this case the probabilities of the formation of the singlet (recombining) state of a... 

Following a cross recombination, it is important to verify that the wavefunction for the newly correlated pair has the correct singlet-triplet probability. For this reason, a separate simulation in which V tot is simulated at all times was also adopted to... 

There is a greater cross-recombination probability in the linear spur structure. This in turn leads to less correlated (S" " / e ) recombining in the singlet state which in turn produces less intersystem crossing from S S yield. 

An individual radical from the RP may encounter a radical from a different RP to fomi what are known as random RPs or F pairs. F pairs which happen to be in the singlet state have a high probability of recombining, so the remaining F pairs will be in the triplet state. Consequently, the initial condition for F pairs is the triplet state in nearly all cases. 

If A is the probability of recombination during a single encounter of a singlet radical pair (close to unity), then the chance of product formation during the second encounter at time t is A Csn( )Pf(0- additional re-encounters, it can be shown that An(<) = A Csn( )P d therefore recombination during the time interval between t and t + dt has a probability Pn(<)d< given by equation (34),... 

In alicyclic hydrocarbon solvents with aromatic solutes, energy transfer (vide infra) is unimportant and probably all excited solute states are formed on neutralization of solute cations with solute anions, which are formed in the first place by charge migration and scavenging in competition with electron solvent-cation recombination. The yields of naphthalene singlet and triplet excited states at 10 mM concentration solution are comparable and increase in the order cyclopentane, cyclohexane, cyclooctane, and decalin as solvents. Further, the yields of these... 

The singlet excited molecules formed in charge recombination may not convert with 100% efficiency to Si as discussed in Sec. 2.1. This effect may be important for smaller molecules for larger molecules such as the decalins or n-dodecane the efficiency is probably very close to unity. 

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