Vibronic sideband

When the first term is nonzero the electronic transition is allowed by a particular mechanism, whereas it is forbidden when zero. It contributes mainly zero phonon line intensity when the shift in equilibrium positions of the nuclei between the two states can be ignored, so that (Zfk Xin)t 0 only for the k=n case in Eq. (17). The second and third terms contribute mainly one-phonon sideband vibronic intensity to the transition. (i/q Me i/r ) 2 is given by [68]... 

Alexandrite, the common name for Cr-doped chrysoberyl, is a laser material capable of continuously tunable laser output in the 700-800 nm region. It was established that alexandrite is an intermediate crystal field matrix, thus the non-phonon emitting state is coupled to the 72 relaxed state and behaves as a storage level for the latter. The laser-emitted light is strongly polarized due to its biaxial structure and is characterized by a decay time of 260 ps (Fabeni et al. 1991 Schepler 1984 Suchoki et al. 2002). Two pairs of sharp i -lines are detected connected with Cr " in two different structural positions the first near 680 nm with a decay time of approximately 330 ps is connected with mirror site fluorescence and the second at 690 nm with a much longer decay of approximately 44 ms is connected with inversion symmetry sites (Powell et al. 1985). The group of narrow lines between 640 and 660 nm was connected with an anti-Stokes vibronic sideband of the mirror site fluorescence. 

The photoconductivity and absorption spectra of the multilayer polydiacetylene are shown in Fig. 22 [150]. The continuous and dotted line relate to the blue and red polymer forms respectively. Interpretation is given in terms of a valence to conduction band transition which is buried under the vibronic sidebands of the dominant exciton transition. The associated absorption coefficient follows a law which indicates either an indirect transition or a direct transition between non-parabolic bands. The gap energies are 2.5 eV and 2.6 eV for the two different forms. The transition is three dimensional indicating finite valence and conduction band dispersion in the direction perpendicular to the polymer chain. 

The temperature dependence of the energy transfer rate Wda is related to a changing occupation of the 2E anti-Stokes phonon sidebands and the 4T2 state. On the contrary, pressure significantly increases the energy separation A between the 4T2 and 2E states, whereas the energy of the zero phonon and the vibronic 2E -> 4A2 transitions of Cr3+ change only weakly with pressure. Thus, pressure almost solely influences the occupation of the 4T2 state and with it its contribution to the energy transfer rate, but does not affect the other contributions connected with the 2E state. 

Bai et al. (2005) observed a phonon sideband with a frequency shift of 40-50 cm-1 located on the low-energy side of the 5Do <- 7Fo zero-phonon line (ZPL) in the 77 K excitation spectrum of Eu3+ Y203 NTs and NWs. However, vibronic sidebands generally appears at the high-energy side of the ZPL in the low-temperature excitation spectra since the vibronic transition involving the creation of a phonon with the annihilation of a photon is much more favored than the annihilation of a phonon at low temperature. The origin of this anomaly sideband remains unknown. 

Z(a)) = <5(a>) + j y(co) is the excitonic self-energy and satisfies KK relations e0 and A assume the previous values. The derived variations of <5(co) and y(ai) are presented in Fig. 2.13. We notice that (5(w), though fairly weak throughout the 0-0 region, reaches values of 20cm" around the phonon sideband, and should therefore be included in quantitative estimations of y(cu).95 We find that y(co) increases between co0 and co0 + 46 cm" crosses a stepwise threshold at a>0 + 46 cm" and then steadily grows to a>0 + 394 cm", where a vibronic study56 would be better suited than the parametrization (2.125). 

The absorption intensity of the 0-1 vibronic sideband is entirely borrowed by HT coupling. The observation that this 0-1 transition is of comparable intensity to the 0-0 transition suggests the feasibility of resonance Raman processes in which both the absorption and emission moments are borrowed. This second-order HT coupling displays itself in the appearance of first overtones and combination bands of non-totally symmetric modes. These are observed extensively in the haem proteins 35). 

A successful instance of empirical correlation was found for the electron-vibrational coupling, between 2Eg and 4A2g-states on Mn4+, entering substitutionally for M in the octahedral sites of Cs2MF6 (M = Si, Ge, Ti, Sn, Zr) and M2SiF6 (M = K, Rb, Cs)121 . The Huang-Rhys number S appears in the intensity of the n th vibronic sideband of a progression as exp (— S)Sn/n . From comparison with his emission data at 80 °K Paulusz found a quadratic dependence of S on the estimated Mn—F distance for both Alg and vibrational modes in the former series of hosts and a virtual constancy for die latter series. 

Abstract A brief review of my work with Carl Ballhausen in 1967-1968 and subsequent work. The assignments of the vibronic sidebands in the emission spectra of chromium ammine complexes are given with some comments on the Jahn-Teller effect in the emissive state. Energy transfer and cross relaxation phenomena are discussed and the shell model for this processes in lanthanide elpasolites is presented... 

If the ZPL is weak, then variable temperature studies can identify its location from hot electronic and vibronic structure, with the latter illustrated in Fig. 10. The vibronic structure can be used to identify certain symmetry types of transition, for example Ti-T2 (Table 4). One viewpoint has been put forward that the spectral interpretation is confused by phonon dispersion in the vibronic sidebands of transitions. However, this complexity of the vibronic structure can in fact be utilized to provide a fingerprint to identify the location of the electronic origin. Where possible, it is more certain to compare both emission and absorption (or excitation) spectra for a particular transition in order to locate the electronic origin. Otherwise, transitions from different emissive states (with different state irreps) can be employed to confirm the symmetries and locations of terminal levels. Whereas other neat systems such as PrCl3 show additional features not present in the electronic spectra of the diluted crystal (LaCl3 Pr3+) due to interactions between... 

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