Nonlinear Raman spectroscopy

One example is intracavity Raman spectroscopy of molecules in a supersonic jet, demonstrated by van Helvoort et al. [327]. If the intracavity beam waist of an argon-ion laser is shifted to different locations of the molecular jet (Fig. 3.12), the vibrational and rotational temperatures of the molecules (Sect. 4.2) and their local variations can be derived from the Raman spectra. 

More details of recent techniques in linear laser Raman spectroscopy can be found in [301, 328]. 

When the intensity of the incident light wave becomes sufficiently large, the induced oscillation of the electron cloud surpasses the linear range assumed in Sect. 3.1. This implies that the induced dipole moments p of the molecules are no longer proportional to the electric field E and we have to generalize (3.2). The function p E) can be expanded into a power series of (n = 0,1,2.), which is generally written 

This gives for the polarization P = Np of a medium with N oriented dipoles 

For sufficiently small electric field amplitudes E the nonlinear terms in (3.18a) can be neglected, and we then obtain (3.2) for the linear Raman spectroscopy. 

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Eckbreth A C 1988 Nonlinear Raman spectroscopy for combustion diagnostics J. Quant. Spectrosc. Radlat. Transfer 40 369-83... 

Dudovich, N., Oron, D., and Silberberg, Y. 2002. Single-pulse coherently controlled nonlinear Raman spectroscopy and microscopy. Nature 418 512-14. 

Ichimura, T., Hayazawa, N., Hashimoto, M., Inouye, Y, and Kawata, S. 2004b. Application of tip-enhanced microscopy for nonlinear Raman spectroscopy. Appl. Phys. Lett. 84 1768-70. 

This chapter describes the application of these techniques to a liquid photolytic reaction. The motivation was the assessment of the capabilities and limitations of single-pulse nonlinear Raman spectroscopy as a probe of fast reactions in energetic materials. 

Here, E is the strength of the applied electric field (laser beam), a the polarizability and / and y the first and second hyper-polarizabilities, respectively. In the case of conventional Raman spectroscopy with CW lasers (E, 104 V cm-1), the contributions of the / and y terms to P are insignificant since a fi y. Their contributions become significant, however, when the sample is irradiated with extremely strong laser pulses ( 109 V cm-1) created by Q-switched ruby or Nd-YAG lasers (10-100 MW peak power). These giant pulses lead to novel spectroscopic phenomena such as the hyper-Raman effect, stimulated Raman effect, inverse Raman effect, coherent anti-Stokes Raman scattering (CARS), and photoacoustic Raman spectroscopy (PARS). Figure 3-40 shows transition schemes involved in each type of nonlinear Raman spectroscopy. (See Refs. 104-110.)... 

Figure 3-40 Transition schemes involved in nonlinear Raman spectroscopy.

A. B. Harvey, ed., Chemical Applications of Nonlinear Raman Spectroscopy, p. 1. Academic Press, New York, 1981. 

Surface-Enhanced Raman Spectroscopy (SERS) Raman Spectroelectrochemistry Time-Resolved Raman (TR-) Spectroscopy Matrix-Isolation Raman Spectroscopy 2D Correlation Raman Spectroscopy Raman Imaging Spectrometry Nonlinear Raman Spectroscopy References... 

Venturo VA, Felker PM. Nonlinear Raman spectroscopy of ground-state intermolecular vibrations in benzene complexes. J Phys Chem 1993 97 4882-4886. 

In this section we first give a survey on the most common nonlinear Raman processes, i. e. the (incoherent) hyper Raman scattering and several forms of coherent nonlinear Raman scattering. We then describe the instrumentation needed to perform several practical kinds of these nonlinear laser spectroscopies. Applications of nonlinear Raman spectroscopy will be found in Sec. 6.1. 

Let us first briefly discuss spontaneous nonlinear Raman spectroscopy on an isolated single molecule. Generally the induced dipole moment p in a molecular system is written in the form... 

Nonlinear Raman spectroscopies based on third-order susceptibilities... 

One of the main advantages of CARS and also of other nonlinear Raman spectroscopies is the high resolution that can be achieved in spectra of gases at low pressures. The reason for this is that the instrumental resolving power in these techniques depends only on the convoluted linewidths of the lasers used for excitation, whereas in linear Raman spectroscopy the resolution is determined by the monochromators used to disperse the observed scattered Raman light. 

The methods of nonlinear Raman spectroscopy, i. e. spontaneous hyper Raman scattering (based on the hyperpolarizability) and coherent nonlinear Raman scattering (based on the third-order-nonlinear susceptibilities) are discussed in detail in Sec. 3.6.1. In Sec. 3.6.2 the instrumentation needed for these types of nonlinear spectroscopy is described. In this section we present some selected, typical examples of hyper Raman scattering (Sec. 6.1.4.1), coherent anti-Stokes Raman. scattering (Sec. 6.1.4.2), stimulated Raman gain and inverse Raman spectroscopy (Sec. 6.1.4.3), photoacoustic Raman spectroscopy (Sec. 6.1.4.4) and ionization detected stimulated Raman spectroscopy (Sec. 6.1.4.5). 

Barrett JJ, Heller DF (1982) In Nonlinear Raman Spectroscopy and its Chemical Applications, Kiefer W, Long DA, (eds). Reidel, Dordrecht, p 563 Barrett JJ, Siebert DR, West GA (1982) In Nonlinear Raman Spectroscopy and its Chemical Applications, Kiefer W, Long DA, (eds). Reidel, Dordrecht, p 585 Barron LD (1976) Raman Optical Activity, Proceedings Vth International Raman Conference, vol 4, no 44, Freiburg, p 677. 

Hartke B, Kiefer W, Kolba E, Manz J, Strempel J (1992) J Chem Phys 96 5636 Hartland GV. Henson BE, Connell LL, Corcoran TC, Fclker PM (1988) J Phys Chem 92 6877 Hartland GV, Henson BE, Venture VA, Hertz RA, Felker PM (1990) J Opt Soc Am B7 1950 Hartland GV, Joireman PW, Connell LL, Felker (1992) J Chem Phys 96 179 Hartman KA, Clayton NW, Thomas GJ Jr (1973) Biochem Biophys Res Comm 50 942 Harvey AB (1981) Chemical Applications of Nonlinear Raman Spectroscopy, Academic Press, New York... 

Kiefer W, Long DA (1982) Nonlinear Raman Spectroscopy and its Chemical Applications, Reidel, Dordrecht... 

Schrotter HW, Berger H, Boquillon JP, Lavorel B, Millot G (1988) High-Resolution Nonlinear Raman Spectroscopy of Rovibrational Bands in Gases. In Salzer R, Kriegsmann H, Werner G (eds) Progress in Molecular Spectro.scopy, Teubner Texte zur Physik, Bd 20. Teubner, Leipzig,... 

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