Half-electron excited singlet states

A similar situation results if emission occurs from one of the excited electronic state reached by internal conversion. The process then would be as that shown in the following figure. Even in this case the emission process that connects the two states has same number of unpaired electrons — two singlet states or two states with half-lives in the range 1(T9-1h4S. 

Fig. 11.7 Pump-probe measurements of stimulated emission from (A) the laser dye IR132 in dimethylsulfoxide, and (B) the lowest excited singlet state of the bacteiochlorophyll dimer that serves as the primary electron donor in reaction centers from Rhodobacter sphaeroides [23]. The excitation flash was centered at 830 nm and had a width at half-maximum amplitude (FWHM) of about 16 fs in both cases. The probe pulse had a FWHM of about 80 fs and was crmtered at 900 nm in (A) and 940 nm in (B). The ordinate scales are arhitrary...

Rauhut and coworkers proposed the occurrence of a charge transfer complex between the HEI and the ACT in order to explain the electronically excited-state generation in the peroxyoxalate system. Chemiluminescence quantum yield (4>cl) measurements with different activators have shown that the lower the ACT half-wave oxidation potential (Ei/2° ) or singlet energy (Es), the higher the electronically excited-state formation rate and 4>cl- According to the mechanistic proposal of Schuster and coworkers for the CIEEL... 

As follows from these results, orbital disproportionation in systems with half-closed-shell electronic configurations is necessarily accompanied by lowering the spin of the electronic ground state. For the configuration it means transition from the high-spin (HS) triplet A state to the low-spin (LS) singlet state A, while for t this transition is from the quadruplet (HS = 3/2) to the doublet (LS = 1/2) state. Since this transition is induced by the PJT distortion originating from an excited... 

Figure 3.7 The principles of one- and two-photon excitation. In one-photon excitation (left) a single photon, whose energy matches the electronic transition between the ground state and first singlet state causes an electron to be excited. Subsequent relaxation of the electron results in fluorescence emission. In two-photon excitation, two photons, each with approximately half the energy of the electronic transition, are absorbed simultaneously resulting in excitation of an electron and subsequent fluorescence.

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