Raman scattering excitation profile

Haynes CL, Van Duyne R. Plasmon scanned surface-enhanced Raman scattering excitation profiles. Material Research Society Symposium Proceedings 2002, 728, S10.7.1-S10.7.6. 

Fi . 8c. Raman scattering excitation profiles, deduced from the intensities of the C=C-stretching modes Vi ( x), Vi (O) v j ( ), for different laser frequencies, and the absorption spectrum of a sixteen layer 6a multilayer after 245 min. UV-irradiation... 

I. Smova-Sloufova, B. Vlckova, T.L. Snoeck, D.J. Stufkens, P. Matejka, Surface-enhanced Raman scattering and Surface-enhanced resonance Raman scattering excitation profiles of Ag-2,2 -bipyridine surface eomplexes and of [Ru(bpy)3] on Ag colloidal surfaces manifestations of the charge-transfer resonance contributions to the overall surface enhancement of Raman scattering. Inorg. Chem. 39, 3551 (2000)... 

RRS has also introduced the concept of a Raman excitation profile (REPy for thefth mode) [46, 4lZ, 48, 49, 50 and M]. An REP. is obtained by measuring the resonance Raman scattering strength of thefth mode as a fiinction of the excitation frequency [, 53]. Flow does the scattering intensity for a given (thefth) Raman active vibration vary with excitation frequency within an electronic absorption band In turn, this has led to transfomi theories that try to predict... 

Kneipp K, Kneipp H and Seifert F 1994 Near-infrared excitation profile study of surface-enhanced hyper-Raman scattering and surface-enhanced Raman scattering by means of tunable mode-locked... 

In the case of polyenes, the term I scattering is dominant in the Raman spectra resonant with the 1 flu excited states22,26 the contribution of the term m scattering is important in the Raman spectra resonant with the 2 Ag excited states27. In addition, an interference effect between the 1 flu and 2 kg states in a Raman-intensity vs excitation-photon-energy plot (which is called an excitation profile) of the in-phase C=C stretch has been suggested28. 

Figure 6.1-5 Stokes transition for continuum resonance Raman scattering in from the initial vibrational state />= 0> to the final state f >= 6> via electronic state B( 77o+). (A) Absolute value of the time overlap < 6 0(t) > as a function of time, (B) excitation profile of this transition [square of the half Fourier transform of < f i t) > as a function of energy] (Ganz and Kiefer, 1993 a).

No overtones or combinations involving more than two quanta are observed, which is consistent with the absence of a 0-2 transition in absorption. The second-order bands in the resonance Raman spectrum of cytochrome c are shown in Fig. 20 (Section 4.8) where they appear in the 1650-3 300 cm region for excitation at 514.5 nm (point F). The excitation profiles of the second-order bands should peak only in the 0-1 absorption region, at positions consistent with the wavenumbers of the relevant fundamentals. This behaviour is expected since the appropriate parts of the scattering tensor show only 0—1 resonance conditions ... 

Thus, in summary, it appears that the LFE mechanism predicts that for dyes in resonance the Raman spectrum will be enhanced to the same degree as normal scatterers, except when a typical resonance excitation profile is not observed. This conclusion is in contradiction to that expressed in Reference 240. The excessive sensitivity of the model presented there to lifetime changes is, to a large part, due to the simple two-state description of the excited... 

It is inappropriate to go into the theory underlying this effect here, but it should be noted that not all Raman-active modes of a sample give enhanced band intensities in RR scattering. The mode selectivity depends on the symmetry of the sample molecule and the nature of its electronic transitions, which are actively involved in the Raman process. Thus, by changing the Raman excitation wavelength from coincidence with one electronic absorption band to another of a different symmetry type, the pattern of vibrational band resonance enhancements may change drastically. This dependence of Raman band intensity on the wavelength of the excitation source is known as the "excitation profile and may also be used to provide information on the nature of the electronic transitions. 

The majority of compounds studied thus far exhibit the A-term rather than the 5-term resonance. A more complete study of resonance Raman spectra involves the observation of excitation profiles (Raman intensity plotted as a function of the excitation frequency for each mode), and the simulation of observed excitation profiles based on theoretical treatments of resonance Raman scattering [113]. 

However, as we noted earlier (in Section II), it is most important to have a full temporal and spatial profile of the picosecond laser pulses in order to correctly interpret the one or two photon excited molecular response functions (absorption, emission, Raman scattering) of the system under study. While autocorrelation techniques such as second harmonic generation (SHG) or two photon fluorescence have always been the route to such short pulse measurements, a significant advance has recently been made in bringing these conventional autocorrelation measurements into the real-time domain. ... 

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... 

Infrared and Raman Spectroscopy. Resonance Raman spectra of aW-trans- and 15-CW-/3-carotene have been compared.The ps resonance Raman spectrum of /8-carotene has been described,and solvent effects on the excitation profile of the line of jS-carotene have been studied. Model calculations have been used to interpret observed jS-carotene Raman spectra and excitation profiles. Raman scattering spectra of j8-carotene-l2 complexes have been determined. Resonance Raman spectra of carotenoids have been used as an intrinsic probe for membrane potential, e.g. neurosporene [7,8-dihydro-(/r,(/r-carotene (183)] in chromatophores of Rhodopseudomonas sphaeroides. ° Resonance Raman spectroscopy and i.r. spectroscopy have been used in studies of the chromophore of visual pigments and visual cycle intermediates and of bacteriorhodopsin and its photocycle intermediates. ... 

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