Phosphorescence band

Preannihilative electrochemical oxidation of the phenanthrene anion has given a green emission13,64 spectrally nearly identical to the previously reported room-temperature phenanthrene phosphorescence which is a single broad peak.71 Chemical oxidation of the chrysene anion with Wurster s blue perchlorate produced an emission containing three bands at 19,800, 18,600, and 17,400 cm"1 which seem to correspond to the known phosphorescence bands of chrysene (19,500,18,500, and 16,600 cm-1). Chemical oxidation of the radical anion of N-methylcarbazole has possibly led to phosphorescent emission from this triarylamine.7... 

The room temperature phosphorescence spectra of benzophenone and its substituted analogues show a weak band about 1600 cm -1 higher in frequency than the first phosphorescence band. Because the temperature dependence of its intensity corresponds to an activation energy approximately equal to the... 

Explanation of Table ET = triplet energy in kcal/mole from O—O phosphorescence band. Je = intersystem crossing yield from sensitized olefin isomerization method. tp - phosphorescence lifetime in a rigid glass at —196° (sec). Repetition of the data compiled by Arnold63 has in general been avoided. 

The ruthenium phthalocyanine complex (54) shows a visible absorption band at 650 nm (6-49,000 cm" ) and a phosphorescence band located at 895 nm. 

Figure 23-14 Potential energy diagram for the ground state S0 and the first excited singlet S, and triplet Tj states of a representative organic molecule in solution. G is a point of intersystem crossing Sj —> T,. For convenience in representation, the distances r were chosen rS() < rSj < rT thus, the spectra are spread out. Actually, in complex, fairly symmetric molecules, rS(. rs < rT and the 0-0 absorption and fluorescence bands almost coincide, but phosphorescence bands are significantly displaced to the lower wavelengths. From Calvert and Pitts,2 p. 274.

In practice, handling Sq- transitions is often simpler (though less satisfactory), since absorption spectra are not normally available and the maxima of the B and BH+ phosphorescence bands must then be used in the Forster cycle. However Sq-Tj absorption spectra can sometimes be obtained, especially if perturbation methods can be used to enhance the singlet to triplet transition probability. For example, Grabowska and Pakula (1966) induced Sq-Tj absorption in a series of nitrogen-containing heterocyclic compounds by the oxygen perturbation method of Evans (1957). Hence, for these compounds, by combination of absorption and phosphorescence spectral results, the 0-0 transitions could be located more accurately. 

In Fig. 7 we recapitulate the spin-averaged Einstein coefficients for the Vegard-Kaplan emission from the lowest vibrational state of the triplet as well as the corresponding values reported by Piper [89]. The relative transition probabilities for different vibronic phosphorescence bands are quite good [26]. The absolute and the relative intensities of the higher vibrations v" are very sensitive to the transition moment curve... 

Vibrational analysis of the benzene phosphorescence bands indicates that the radiative activity is induced predominantly by e2g vibrations [155, 156]. A weak but observable activity of b2g vibrations has also been found [156, 155, 157]. By introducing spin-orbit- and vibronic coupling through second order perturbation theory Albrecht [158] showed that the vibronic interaction within the triplet manifold is responsible for the larger part of the phosphorescence intensity. This also follows from comparison of the vibrational structure in phosphorescence and fluorescence spectra [159]. The benzene phosphorescence spectrum in rigid glasses [155] reveals a dominant vibronic activity of... 

Finally the intensity of the vibronic phosphorescence band is determined by... 

Hamiltonian is taken into account. In this case only vibronic phosphorescence bands (u = 0—m/=1) appear through non-totally symmetrical b g and ezg vibrations as follows from the scheme given in Fig. 7 and as discussed in the previous section. Their transition moments are equal to (in a.u.) ... 

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