Electronic Raman scattering

Electronic Raman scattering originates not only from free electron excitations, but also from collective electron excitations in the form of plasmons. So far, these two types of excitation have been observed only in conventional semiconductors and to some extent in high temperature superconductors, as discussed in subsections 4.8.4 and 4.8.5. However, doped polymers with not too high carrier concentrations or charge transfer systems are possible candidates, and the search for electronic Raman scattering in such systems is one of the challenges in this held. 

Figure 4.8-23 Raman lines for the ai-0(2,3) mode of ErBa2Cut07 as measured above and below Tc, according to FriedI et al., 1990 (a) and electronic Raman scattering of single crystal YBa2Cu307 at various temperatures and after subtraction of phonon lines, according to Hackel, 1990, (b).

As mentioned, in UFDMEF conditions, the spectral profile is mostly independent of the molecule, and could therefore account for the lower energy peak of the SERS continuum observed in Ref. [14] (previously attributed to electronic Raman scattering or to LSP luminescence). 

In the Raman spectra of Si, the line shape of the optical phonon peak is quite sensitive to degenerate p-type doping as a result of interference of Raman scattering from a continuum of electronic intravalence band transitions (electronic Raman scattering) with that from discrete phonon excitations (vibrational or phonon... 

It is readily shown that this is identically equal to the electronic Raman scattering tensor for the Raman transition /> <- 0>. Note that the first term in Eq. (5.15) dominates if there exists a state r> such that Ef xhco the second term dominates if there is a state such that ,o Such cases lead to resonance enhancement and will be discusse[Pg.57]

Transition from 2F5/2r 7 Energy (cm"1) Electronic Raman scattering intensity1 Observed Theoretical JOA-1 JOA-2 Direct... 

More recent interest has focused upon the interpretation of the relative intensities of the electronic Raman transitions. The theory of electronic Raman spectroscopy has been well-summarized elsewhere [63, 202], and the electronic Raman scattering amplitude from an initial i/rf) to a final jfj) vibronic state (where the phonon states are the same, and usually zero-phonon (i.e. electronic) states) is given by (i/ r czpCF In this expression, the cartesian polarizations of the incident photon (hcv) and the scattered photon (hcvs) are a and p, respectively. The Cartesian electronic Raman scattering tensor is written as... 

Other features of interest in the electronic Raman spectra of these systems [91] are the occurrence of an excited-state electronic Raman transition in Cs2NaTmCl6 when the excited state is thermally populated and of D-term [63] resonance electronic Raman scattering. 

Becker PC, Williams GM, Edelstein N, Koningstein JA, Boatner LA, Abraham MM (1986) Resonance electronic Raman scattering in erbium phosphate crystals. Optics Lett 11 282-284. 

Wickham DG (1963) Use of lead pyrophosphate as a flux for crystal growth. J Appl Phys 33 3597-98 Williams GM, Becker PC, Conway JG, Edelstein N, Boatner LA, Abraham MM (1989a) Intensities of electronic Raman scattering between crystal-field levels of Ce in L11PO4 Nonresonant and near-resonant excitation. Phys Rev B 40 4132-4142... 

Williams GM, Becker PC, Edelstein N, Boatner LA, Abraham MM (1989b) Excitation profiles of resonance electronic Raman scattering in ErP04 crystals. Phys Rev B 40 1288-1296 Williams GM, Edelstein N, Boatner LA, Abraham MM (1989c) Anomalously small Af-5d oscillator strengths and 4/-4/electronic Raman scattering cross sections for Ce in crystals of LUPO4. Phys Rev 6 40 4143-4152... 

The ODMR technique we have reviewed in this chapter uses spin-depen-dent properties of semiconductors. Therefore, this technique can be extended to other optical phenomena than luminescence and photoinduced absorption such as treated here, e.g., electronic Raman scattering (Romes-tain et al, 1974 Geschwind, 1978), optical absorption (Mollenauer et al, 1969) etc. Since the pioneering work by Lepine (1972) on crystalline silicon. 

Electronic Raman scattering in 4. Light scattering from phonon ... 

The ground state of Sm " in the Sm monochalcogenides is 4f ( F = 0,1,.. . , 6), with a 0.6 eV wide spin-orbit-split multiplet. Electronic Raman scattering from the different /-multiplet levels of cleaved (100) faces of semiconducting SmSe (Guntherodt et al. 1981a) is shown in fig. 2. The odd-/ levels show up for perpendicular incident ( ,) and scattered (Ej polarization vectors, where-... 

Fig. 2. Electronic Raman scattering from the (Sm ) 4f ( F ) configuration of SmSe at 80 K under 5145 A laser excitation using backscattering from a cleaved (100) face ) l , F +4rjj ...

Fig. 3. Electronic Raman scattering from the /-multiplet levels of Smj Yj.Se at 80 K for sl.O for = 0.05, the La-substituted Sm jjLao ojSe is shown. The scattering configuration is the same as in fig. 2. The hatched area indicates the electronic scattering from the J-0-> 1 excitation. Phonon scattering is seen below 200 cm ...

Electronic Raman scattering in EuPd.2Si2 and EuCu2Si2... 

Fig. 5. Raman spectra of EuPd2Si2 at different temperatures under 5309 A laser excitation. Vertical dashed guide lines mark the intraconfiguration-al excitations (Et.int.a) he Eu 4f ( F2) configuration solid lines through spectra are guide lines to the eye. Top of the figure electronic Raman scattering due to the Sm 4f ( F2) configuration of SmSe.

Fig. 7. Schematic representation of the electronic Raman scattering process in an intermediate-valence Eu compound showing an interconfigura-tional excitation energy , 0. Indicated are the in/raconflgurational energy losses ( L,imra) snd the interconflgurational energy losses ( l,inter =...

Electronic Raman scattering experiments on oriented single-crystal samples of CeCu2Si2 were performed by Cooper et al. (1986) using a polarized 4880 or 5145 A line of an argon laser as an excitation source. 

If the frequency difference o)l — corresponds to an electronic transition of the molecule, we speak of electronic Raman scattering [312, 313], which gives complementary information to electronic-absorption spectroscopy. This is because the initial and final states must have the same parity, and therefore a direct dipole-allowed electronic transition /) f) is not possible. 

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