Non-linear Raman spectroscopy

Laubereau A 1982 Stimulated Raman scattering Non-Linear Raman Spectroscopy and its Chemical Applications ed W Kiefer and D A Long (Dordrecht Reidel)... 

A. B. Harvey, ed., Chemical Applications of Non-linear Raman Spectroscopy, Academic Press, New York, 1981. 

Thus far, we have reviewed basic theories and experimental techniques of Raman spectroscopy. In this chapter we shall discuss the principles, experimental design and typical applications of Raman spectroscopy that require special treatments. These include high pressure Raman spectroscopy, Raman microscopy, surface-enhanced Raman spectroscopy, Raman spectroelectro-chemistry, time-resolved Raman spectroscopy, matrix-isolation Raman spectroscopy, two-dimensional correlation Raman spectroscopy, Raman imaging spectrometry and non-linear Raman spectroscopy. The applications of Raman spectroscopy discussed in this chapter are brief in nature and are shown to illustrate the various techniques. Later chapters are devoted to a more extensive discussion of Raman applications to indicate the breadth and usefulness of the Raman technique. 

If coherent radiation with a very high intensity is applied continuously or as pulse, non-linear effects can be observed which produce coherent Raman radiation. This is due to the quadratic and cubic terms of Eq. 2.4-14, which describe the dipole moment of a molecule induced by an electric field. Non-linear Raman spectroscopy and its application are described in separate chapters (Secs. 3.6 and 6.1), since this technique is quite different from that of the classical Raman effect and it differs considerably in its scope. 

Schrotter HW (1982) In Kiefer W, Long DA (eds) Non-linear Raman Spectroscopy and its Chemical Applications. D Reidel, Dordrecht, p 143... 

W. Kiefer, Non-linear-Raman Spectroscopy, Applications, in Encyclopedia of Spectroscopy and Spectrometry, Vd. 2, Academic Press, San Diego 2000,... 

Kiefer, W., and Long, D.A., eds., Non-Linear Raman Spectroscopy and its Chemical Applications, Reidel, Dordrecht, 1982. 

A.C. Eckbreth, P.W. Schreiber Coherent anti-Stokes Raman spectroscopy (CARS) Applications to combustion and gas-phase diagnostics, in Chemical Applications of Non-Linear Raman Spectroscopy, ed. by A.B. Harvey (Academic, New York 1981)... 

HW Schrotter, H Berger, JP Boquillon, B Lavorel, G Millot. High-resolution non-linear Raman spectroscopy of rovibrational bands in gases. J Raman Spectrosc 21 781-789, 1990. 

W Kiefer, DA Long, eds. Non-Linear Raman Spectroscopy and Its Chemical Applications. Dordrecht Reidel, 1982. 

B Lavorel, G Millot, M Rotger, G Rouill6, H Berger, HW Schrotter. Non-linear Raman spectroscopy in gases. J Mol Struct 273 49-59, 1992. 

Here we have described two second-order non-linear spectroscopies, SFG in detail and hyper-Raman scattering briefly. 

Raman spectroscopy has been widely used to study the composition and molecular structure of polymers [100, 101, 102, 103, 104]. Assessment of conformation, tacticity, orientation, chain bonds and crystallinity bands are quite well established. However, some difficulties have been found when analysing Raman data since the band intensities depend upon several factors, such as laser power and sample and instrument alignment, which are not dependent on the sample chemical properties. Raman spectra may show a non-linear base line to fluorescence (or incandescence in near infrared excited Raman spectra). Fluorescence is a strong light emission, which interferes with or totally swaps the weak Raman signal. It is therefore necessary to remove the effects of these variables. Several methods and mathematical artefacts have been used in order to remove the effects of fluorescence on the spectra [105, 106, 107]. 

W. Hug, Instrumental and Theoretical Advances in Raman Optical Activity, in Raman Spectroscopy, Linear and Non-Linear , J. Lascomb and P. Huong (eds), Wiley-Heyden, Chichester, 1982 p. 3. 

Pulsed laser-Raman spectroscopy is an attractive candidate for chemical diagnostics of reactions of explosives which take place on a sub-microsecond time scale. Inverse Raman (IRS) or stimulated Raman loss (.1, ) and Raman Induced Kerr Effect (2) Spectroscopies (RIKES) are particularly attractive for singlepulse work on such reactions in condensed phases for the following reasons (1) simplicity of operation, only beam overlap is required (2) no non-resonant interference with the spontaneous spectrum (3) for IRS and some variations of RIKES, the intensity is linear in concentration, pump power, and cross-secti on. 

Vibrational sum-frequency spectroscopy (VSFS) is a second-order non-linear optical technique that can directly measure the vibrational spectrum of molecules at an interface. Under the dipole approximation, this second-order non-linear optical technique is uniquely suited to the study of surfaces because it is forbidden in media possessing inversion symmetry. At the interface between two centrosymmetric media there is no inversion centre and sum-frequency generation is allowed. Thus the asynunetric nature of the interface allows a selectivity for interfacial properties at a molecular level that is not inherent in other, linear, surface vibrational spectroscopies such as infrared or Raman spectroscopy. VSFS is related to the more common but optically simpler second harmonic generation process in which both beams are of the same fixed frequency and is also surface-specific. 

UV resonance Raman spectroscopy (UVRR), Sec. 6.1, has been used to determine the secondary structure of proteins. The strong conformational frequency and cross section dependence of the amide bands indicate that they are sensitive monitors of protein secondary structure. Excitation of the amide bands below 210 nm makes it possible to selectively study the secondary structure, while excitation between 210 and 240 nm selectively enhances aromatic amino acid bands (investigation of tyrosine and tryptophan environments) (Song and Asher, 1989 Wang et al., 1989, Su et al., 1991). Quantitative analysis of the UVRR spectra of a range of proteins showed a linear relation between the non-helical content and a newly characterized amide vibration referred to as amide S, which is found at 1385 cm (Wang et al., 1991). 

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