Singlet and triplet states of the

Table 2 Energy differences between the lowest singlet and triplet states of the trimethylene-based 1,3-diradicals calculated by (6,6)CASSCF and (6,6) CAS-MP2 methods with the 6-3IG basis sets...

Frosch(84,133) have explained the external heavy-atom effect in intersystem crossing by postulating that the singlet and triplet states of the solute, which cannot interact directly, couple with the solvent singlet and triplet states, which themselves are strongly coupled through spin-orbit interaction. Thus the transition integral becomes<134)... 

Several carbonyl-containing peroxide additives have been shown to increase the initial rate of the nonoxidative photo-dehydrochlorination of PVC (54). In studies with polymeric ketones unrelated structurally to PVC, the excited singlet and triplet states of the carbonyl groups in these polymers were found to sensitize 0-0 homolysis at rates approaching diffusion control (55). Similar reactions may well occur in oxidized vinyl chloride polymers. 

The simple reaction scheme outlined in Scheme 2 easily accommodates the results obtained in the investigation of XA. The basic scheme is just the same as it is for BA except that the relative energies of the singlet and triplet states of the carbene are reversed. All of the evidence points to a singlet ground state for XA. This includes the absence of an epr signal, the nearly diffusion-controlled formation of ether in direct and sensitized experiments, the stereospecific cyclopropanation, and the absence of a rapid reaction of the carbene with 02. 

It has been suggested that this increase in yield is due to the heteroatom which reduces the energy difference between the singlet and triplet states of the common, biphenyl nucleus. - - The lifetime and quantum yields of triplet state formation have been measured at 25° and interpreted in the context of spin-orbital coupling. -... 

Figure 5. Estimated transition energies of low-lying excited singlet and triplet states of the 5.35 Cl -MgP-P dimer. Si and S3 correspond to mixtures of localized states S2 and Ss correspond to iCTi and ICT2, respectively T1-T7 and Tg correspond to localized states and Ts...

Reaction (69) takes place via the , singlet and triplet states of the ketone (Kellmann and Dubois, 1965). Using what are commonly termed Salem diagrams, Salem (1974) illustrated the manner in which the excited , state of the reactants correlates smoothly with the ground state products this is illustrated in Fig. 15. The surface crossing that is indicated is... 

The singlet and triplet states of the antiaromatic D5h SisH5+ (153) are not minima on the Si5H5+ PES. When the D5h symmetry of the singlet is released, it first collapses to the C2V isomers 154 and 155 which are also not minima on the PES, and upon release of the C2v constraints they further collapse to the Cs structure 156, which is the only minimum on the Si5H5+ PES. The pentasila-allylic-type cation 156, which has a structural... 

What is the difference between singlet and triplet states of the excited thymine molecule Why do triplet precursors play a more important role in thymine dimerization in solutions than in films ... 

The energies of the singlet and triplet states of the simple molecules CH2 [8, 9] and SiH2 [10, 11] are well established from both theoretical and experimental studies. The singlet-triplet promotion energy, s-t> is +8.7 for CH2 and -21 kcal mol" for SiH2, a difference of-30 kcal mol". ... 

Schmidt, R. and Brauer, H.-D. (1971). The energetic positions of the lowest singlet and triplet state of the Schlenk and of the Muller hydrocarbon. Angew. Chem. Int. Ed. 10, 506-507... 

Hehre, W.J. Pople, J.A. Lathan, W.A. Radom, L. Wasserman, E. Wasserman, Z.R. Molecular orbital theory of the electronic structure of organic compounds 28. Geometries and energies of singlet and triplet states of the C3H2 hydrocarbons. J. Am. Chem. Soc. 1976, 98, 4378-4383. 

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