Benzene transitions from higher

In addition to transitions in the ir manifold discussed above, some attention has been given recently to possible o-ir states in the ultraviolet nonradlative transitions from the B2jj state. Callomon et al. (27) have postulated the transitions from higher vibrational levels of B2y to a E2u(high resolution absorption spectrum of vapor phase benzene in the 5.0 eV region. initio (12,28) calculations have predicted the presence of at least one a state (e2 ) lying between two filled ir-molecular orbitals. Photoionization (29,30) experiments, and other evidence (31) appear to agree with the conclusion that a-o-ir transition may be... 

Recently, the effect of pressure-induced luminescence rigidochromism on the emission behavior of 4a has also been reported [58], In ambient pressure, the emission of the complex occurs at 695 nm in benzene. However, at a pressure higher than that required to induce the solvent to undergo the room temperature phase transition from fluid to solid, the emission band shifts to 575 nm, which is similar to the solid state emission wavelength (580 nm) of the complex. 

M (0) is nonzero only if the electronic transition is intrinsically El-allowed (as in the aniline Sj <- Sq system or in the second allowed system of SO2). It is small for the naphthalene Sj <- Sq system, and it vanishes for the So transition in an isolated benzene molecule. In the latter two molecules, intense vibrational bands can thus arise only from the first-order term (or in principle from higher-order terms) in Eq. 7.11. HT theory retains only the first-order term in Eq, 7.11. If is a nontotally symmetric mode having the same frequency and equilibrium value in both electronic states m and n, the Franck-Condon amplitude vanishes by symmetry unless the number of quanta in mode... 

Figure 7. Experimental data (symbols) for TNB s viscosity [78] superimposed on the results of the fitting procedure (line) from Lubchenko and Wolynes [47] are shown. Ta is diown by a tickmark. (TNB = trinaphthyl benzene). The temperature Ter signifies a crossover from activated to collisional viscosity, dominant at the lower and higher temperatures, respectively (see text). The temperature is varied between the boiling point and the glass transition. The right-hand side panel depicts the temperature dependence of the length scales of cooperative motions in the liquid. The thick solid and dashed lines are the critical radius and the cooperativity length respectively. Taken from Ref. [47] with permission.

Solvent — The transition energy responsible for the main absorption band is dependent on the refractive index of the solvent, the transition energy being lower as the refractive index of the solvent increases. In other words, the values are similar in petroleum ether, hexane, and diethyl ether and much higher in benzene, toluene, and chlorinated solvents. Therefore, for comparison of the UV-Vis spectrum features, the same solvent should be used to obtain all carotenoid data. In addition, because of this solvent effect, special care should be taken when information about a chromophore is taken from a UV-Vis spectrum measured online by a PDA detector during HPLC analysis. 

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