No-phonon line, .

The widths of the phonon replicas I (1) and /2 (1) are only 2-4 times larger than the no-phonon lines, and this implies a relatively small coupling with the electronic transitions, which has been discussed by Kleverman et al. [100] in terms of a pseudolocalized phonon in the vicinity of the acceptor atom. The positions of the no-phonon acceptor lines of Au and Pt and of the phonon replicas of Pt in silicon are given in Table 7.18. 

Figure 4.10(b) shows the temperature dependence of the absorption spectrum expected for an indirect gap. It can be noted that the contribution due to becomes less important with decreasing temperature. This is due to the temperature dependence of the phonon density factor (see Equation (4.37)). Indeed, at 0 K there are no phonons to be absorbed and only one straight line, related to a phonon emission process, is observed. From Figure 4.10(b) we can also infer that cog shifts to higher values as the temperature decreases, which reflects the temperature dependence of the energy... 

Fig 4 Energy levels of Ce3+ incorporated in (a) YP04, (b) CaF2, and (c) LiYF4, after van Pieterson et al (200 The position of the zero phonon line is given. For those levels in which no zero phonon line was observed, they been estimated as constant displacements from the maxima of the observed vibronic bands. 

Fig. 6.6. PLE spectrum of the P BE due to the absorption of laser radiation tuned over the absorption range of the P BE no-phonon (Xi line near 1150 meV in a qmi silicon sample enriched at 99.991% with 28Si. The large bracket at the bottom corresponds to the 486 neV hyperfine splitting of the ground state of the P donor atom. For the two smaller brackets, see text [273]. Copyright 2006 by the American Physical Society...

Further investigations were conducted to determine the quality of the standard and RIE etched porous SiC samples using LTPL analysis, again performed by the group of W.J. Choyke at the University of Pittsburgh. The photoluminescence intensity of the 3C-SiC epilayers increased approximately ten and five times that of the standard 3C-SiC for the 52 and 72 pm thick RIE etched porous 3C-SiC substrates, respectively. In addition, the no-phonon nitrogen bound exciton Nc line... 

In n-conjugated polymers no zero-phonon lines have been observed in SSF spectra, indicating that there is always some chain relaxation in response to optical excitations [17, 59]. The magnitude of this effect should and, in fact, does depend on the rigidity of the chain. In PPV the residual Stokes shift is on the order of 100 cm-1, while in MeLPPP it is —20 cm-1 only [21]. In the time domain the former value corresponds to a dephasing on the order of 100 fs as has been verified by experiments on fs-wave-packet fluorescence interferometry on tail states of PPV [60]. 

The latter statement can be illustrated as follows. AVhen AR = 0, the vibrational overlap will be maximal for the levels v = 0 and v = 0, since the vibrational wave functions involved have their maxima at the same value of R, viz. R . The absorption spectrum consists of one line, corresponding to the transition from v = 0 to v = 0. This transition is called the zero-vibrational or no-phonon transition, since no vibrations are involved. If, however, AR 0, the v = 0 level will have the... 

The experiments on phycobilisomes did not give evidence for exciton-like energy transport. In particular, no specific dependence of the zero-phonon line width as a function of bum frequency could be found, a result which was considered as strong support for stochastic transport processes. 

The PL spectrum obtained at 20 K from the dots deposited on the patterned area shows weak wetting layer PL and an intense signal from the Ge islands, having a rather narrow line width and no-phonon and TO-phonon lines well separated. The modified wetting layer PL emission from the patterned area, is most likely due to non-planar shape of the area inbetween the Ge islands varying the thickness and orientation of the wetting layer. Apparently the carriers are more effectively collected in the regimented islands. The narrow line width of the dot... 

In contrast to CePdj, up until now, no phonon anomalies, such as unusual line shifts or line widths, have been observed in CeSnj. Nevertheless, we present in fig. 42 the results of a thorough investigation of the dispersion curves of CeSnj and, for comparison, of LaSnj at room temperature by Pintschovius et al. (1980, 1983). The... 

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