T - So Absorption

Fig. 6.1 The Davydov splitting Aq = 21.5 cm of the 0.0-transition in the T] So absorption spectrum of anthracene at 300 K. This is the excitation spectrum of the triplet excitons. The absorption was detected via the intensity of the delayed fluorescence...

Fig. 14. Sn So and Tm t- Tl absorption spectra of anthracene in alcohol at 113 K (From Meyer, Astier, and Leclercq, Ref. O))...

An estimate of the T, lifetime can be made from the measured line width of the Ti < So absorption. Figure 2.18 presents the SitO0) T O0) S0(Oo) OODR spectrum measured under medium-frequency resolution ( 0.05 cm-1) [29]. The rotational structure, depicted in Figure 2.18 consists of a prominent band with two satellites (50 times weaker) at 6 cm 1 to lower energies. From... 

In contrast to polyenes the aromatic molecules exhibit not only the Ti — So absorption, but also the longlived T — So emission, which gives rise to phosphorescence phenomena of rigid solvents and crystals. This is another important field of applications of spin-orbit quadratic response theory. Such calculations refer to lifetimes, transition moments, oscillator strengths and polarization directions for the radiative decay of molecular triplet states. These quantities may either be averaged over the triplet levels or refer to specific triplet spin sublevels depending on the conditions for the relevant experimental measurements. 

Fig. 3.16 Modified Jablonski diagram visualizing radiative, non-radiative and photoproduct forming processes (adopted from Braun et al., 1991 and Pfoertner, 1998). The lifetimes of the individual processes are given in parentheses. 1, Absorption (excitation) So->82 and 2, absorption Sq->S, (10 s) 3, fluorescence S, ->So + hVf (10 -10 s) 4, phosphorescence T, ->So -H hvph (10 -10 s) 1C internal conversion S2->S] + heat (10" -10" s) and...

This isn t so serious if the used catalyst from alkylation is sent to the SARP recovery section. In some cases, the size of the reactor is determined by the amount of cooling surface required for the design temperature. With SARP not as much cooling is required in the alkylation reactor, since part of the heat of the alkylation reaction is evolved in the absorption section. It has been estimated that 50% or more of the heat of alkylation is in the absorption step. 

Lesclaux etal. [86] used flash-photolysis u.v. absorption to follow reactions (47) and (48) between 373 and 573 K. In particular, the presence of polar gases did not affect the derived rate constants and no pressure effect was apparent in contrast to behaviour observed for the HO2 -H HO2 reaction at these temperatures. They reported (/c 47a + 4 b) = 1-3 x 10 exp(365/T) cm molecule" s with = 45 exp(-1465/T), so that /c47a dominates above about 500 K. They also reported /c48 = 4.3 X 10 exp(780/T)... 

The conductivities of these crystals lie typically in the range of 1(T to 10 Q cm clearly higher than those of pure anthracene crystals, for example. Their ground states, as shown by photoelectron spectra, are similar to anthracene, with 5-10% CT character. The triplet states Ti are likewise similar to anthracene, as seen in their optical spectra. The Si <- So absorption is, however, very different it is a typical CT absorption. As its photoconductivity shows, the charge separation in anthracene-PMDA takes place in the Si state with an activation energy of 0.14 eV. 

The UV absorption maxima of all tocopherols lie within the range 292-298 m t, so that the individual determination of tocopherols in mixtures is impossible without previous separation. This method is suitable, however, for assaying the tocopherol content of a preparation which contains only a single tocopherol, e.g., for determining the df-a-tocopherol content of a synthetic product. 

The particular kind of relaxation discusssed above becomes ineffective at higher temperatures, T>T, so that the enhanced absorption decreases. At low temperatures, deformation of the ASR by the sound wave has no great effect on the... 

Si <- Sq spectrum should exhibit the long-axis polarization of the intrinsic S -t- So Ag) transition. All of these band polarizations have been confirmed by obtaining absorption spectra of napthalene doped as an impurity into host crystals, where the napthalene orientations relative to the crystal axes are independently known. 

By means of DFT and TD-DFT calculations, we have evaluated theoretically both the So —> (optical absorption) and the T —> So (phosphorescence) vertical... 

Various primary processes induced upon photon absorption by this molecule are also shown in Fig. 2-1. The photon absorption processes associated with the vibrational-electronic transitions from So to Si and S2 are represented by So —>S Abs. and So - S2 Abs., respectively. By internal conversion (IC) we mean a radiationless process between two different electronic states of the same spin multiplicity. In Fig. 2-1, IC from S2 to S and IC from Si to So are shown. Usually, the rate constants of S2 —>Si IC and Si — So IC are more than lO s" and 10 -10 s" , respectively. By intersystem crossing (KC) we mean a radiationless process between two different electronic states of two different spin multiplicities. In Fig. 2-1, Si Ti ISC and T ->So ISC are shown. The rate constants of the... 

In many molecules absorption of light leads to ionic dissociation. The relative ease of ionization of different states (i.e., S , T , SO is obviously related to the electron density distributions of these states. In the following discussion emphasis will be placed on systems for which comparison of the properties of ground and excited states may be made. 

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