Self-trap

Such renormalization can be obtained in the framework of the small polaron theory [3]. Scoq is the energy gain of exciton localization. Let us note that the condition (20) and, therefore, Eq.(26) is correct for S 5/wo and arbitrary B/ujq for the lowest energy of the exciton polaron. So Eq.(26) can be used to evaluate the energy of a self-trapped exciton when the energy of the vibrational or lattice relaxation is much larger then the exciton bandwidth. 

Plaskett, J. S., Phil. Mag. 45, 1255, "Self-trapped electrons in metals."... 

Emission spectra at these points are shown in Figure 8.2d. The band shapes were independent of the excitation intensity from 0.1 to 2.0 nJ pulse . The spectrum of the anthracene crystal with vibronic structures is ascribed to the fluorescence originating from the free exdton in the crystalline phase [1, 2], while the broad emission spectra of the pyrene microcrystal centered at 470 nm and that of the perylene microcrystal centered at 605 nm are, respectively, ascribed to the self-trapped exciton in the crystalline phase of pyrene and that of the a-type perylene crystal. These spectra clearly show that the femtosecond NIR pulse can produce excited singlet states in these microcrystals. 

Nishimura, H., Yamaoka, T., Hattori, K., Matsui, A. and Mizuno, K. (1985) Wavelength-dependent decay times and time-dependent spectra of the singlet-exciton luminescence in anthracene crystals./. Phys. Soc. Jpn., 54, 4370-4381. Matsui, A. and Nishimura, H. (1980) Luminescence of free and self trapped excitons in pyrene. J. Phys. Soc. Jpn., 49, 657-663. 

Issac, A., Borczyskowski, C. V. and Cichos, F. (2005) Correlation between photoluminescence intermittency of CdSe quantum dots and self-trapped states in dielectric media. Phys. Rev. B, 71, 161302 (R)-l-161302(R)-4. 

If benzyne is produced under conditions where there is no suitable species for it to react with, then it dimerises ( self-trapping ) very rapidly to the stable biphenylene (105) ... 

S.L. Dexheimer, in Coherent Vibrational Dynamics of Exciton Self-Trapping in Quasi-One-Dimensional Systems, ed. by S. De Silvestri, G. Cerullo, G. Lanzani. Coherent Vibrational Dynamics (CRC, Boca Raton, 2007), p. 223... 

Using a high-resolution spectrograph and a Fabry-Perrot interferometer, Gunther eta/. 727) resolved a number of equidistant components with a mean separation of 0.04 cm" in the stimulated Raman spectrum of CSj, which can be attributed to resonant modes in single medium-scale filaments of self-trapped radiation within the liquid. 

A self-trapping mechanism for singlet and triplet excitons, ascribed to... 

It has been shown theoretically that an extra electron or hole added to a one-dimensional (ID) system will always self-trap to become a large polaron [31]. In a simple ID system the spatial extent of the polaron depends only on the intersite transfer integral and the electron-lattice coupling. In a 3D system an excess charge carrier either self-traps to form a severely locahzed small polaron or is not localized at all [31]. In the literature, as in the previous sections, it is frequently assumed for convenience that the wavefunction of an excess carrier in DNA is confined to one side of the duplex. This is, of course, not the case, although it is likely, for example, that the wavefunction of a hole is much larger on G than on the complementary C. In any case, an isolated DNA molecule is truly ID and theory predicts that an excess electron or hole should be in a polaron state. 

The smaller value of i found experimentally suggests that the coupling constant g is larger than we assumed. In our model of DNA we considered hole self-trapping due to interaction with longitudinal vibrations only. As discussed in Sect. 2.1, other degrees of freedom may also contribute to the coupling constant. 

The energy E will necessarily have this minimum, but its value at this point can be positive or negative only in the latter case will a stable self-trapped particle (i.e. a small polaron) form. This is most likely to occur for large effective mass, and thus for holes in a narrow valence band or for carriers in d-bands. If the polaron is unstable then there is practically no change in the effective mass of an electron or hole in equilibrium in the conduction or valence band. 

It will be seen that a barrier exists resisting self-trapping this has been observed as a time delay by Laredo et al (1981,1983) for holes in AgCl, indicating a barrier height of 1.8 meV. 

The carrier can move, either by excitation out of this self-trapped state into the conduction band, or by hopping to a neighbouring site. For hopping to occur, the interatomic distances between two adjacent pairs must be equal, as illustrated in Fig. 2.3(b). Then the electron can move freely from one such pair to the other. Possibly the electron can move backwards and forwards several times before the system relaxes the transition is then adiabatic. Alternatively the chance of transfer in the time during which the configuration persists may be small. 

The triangular planar (D3h symmetry) CO/ molecular ion with 24 electrons (AB324-type) in CaC03 is easily ionized by radiation to electron and hole centres self-trapped in the lattice or an oxygen vacancy type C02 molecular ion at the anon site. Molecular orbital schemes based on the general scheme of AB3 molecules with 25,24 and 23 electrons for atoms A (B, C, Si, N, P, As and S) and B (O) characterize their specific -factor. Hence, the anisotropic -factor of these radicals estimated from the powder spectrum has been to identify the radical species.1... 

Hole centre, COT A self trapped hole forms a planar molecule, C03 (D3h symmetry) with 23 electrons (AB323 -type) gives... 

Trapped electron et A self-trapped electron like an F centre in alkali halides is observed at g = 2.001 with a linewidth of 4.3 mT mostly in glassy ice doped with alkaline ions. 

Nonlinear spectroscopy study of vibrational self-trapping in hydrogen bonded crystals... 

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