Nonlinear Raman scattering spectroscopy

Lim, S. H., Gaster, A. G., and Leone, S. R. 2005. Single-pulse coherently controlled nonlinear Raman scattering spectroscopy. Phys. Rev. A 72 0418031. 

Nonlinear Raman scattering spectroscopy is a multiphoton spectroscopy that enables access to vibrationally excited molecular levels. Through nonlinear optical processes, this technique allows us to study rich molecular information which cannot be reached by linear optical method. 

Nonlinear Raman Scattering Spectroscopy for Carbon Nanomaterials... 

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. 

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). 

D. A. Long, Raman Spectroscopy , McGraw-Hill, New York, 1977. The most comprehensive, unified and fully illustrated treatment of the basic theory and physical principles of Raman, resonance Raman and nonlinear Raman scattering. Readers will be inspired by the elegance and information content of the technique to delve further into the book. 

Depending on the relative phase difference between these temis, one may observe various experimental spectra, as illustrated in figure Bl.5.14. This type of behaviour, while potentially a source of confiision, is familiar for other types of nonlinear spectroscopy, such as CARS (coherent anti-Stokes Raman scattering) [30. 31] and can be readily incorporated mto modelling of measured spectral features. 

Similarly, the first-order expansion of the p° and a of Eq. (5.1) is, respectively, responsible for IR absorption and Raman scattering. According to the parity, one can easily understand that selection mles for hyper-Raman scattering are rather similar to those for IR [17,18]. Moreover, some of the silent modes, which are IR- and Raman-inactive vibrational modes, can be allowed in hyper-Raman scattering because of the nonlinearity. Incidentally, hyper-Raman-active modes and Raman-active modes are mutually exclusive in centrosymmetric molecules. Similar to Raman spectroscopy, hyper-Raman spectroscopy is feasible by visible excitation. Therefore, hyper-Raman spectroscopy can, in principle, be used as an alternative for IR spectroscopy, especially in IR-opaque media such as an aqueous solution [103]. Moreover, its spatial resolution, caused by the diffraction limit, is expected to be much better than IR microscopy. 

Hyper-Raman spectroscopy is not a surface-specific technique while SFG vibrational spectroscopy can selectively probe surfaces and interfaces, although both methods are based on the second-order nonlinear process. The vibrational SFG is a combination process of IR absorption and Raman scattering and, hence, only accessible to IR/Raman-active modes, which appear only in non-centrosymmetric molecules. Conversely, the hyper-Raman process does not require such broken centrosymmetry. Energy diagrams for IR, Raman, hyper-Raman, and vibrational SFG processes are summarized in Figure 5.17. 

Raman spectroscopy comprises a family of spectral measurements based on inelastic optical scattering of photons at molecules or crystals. It involves vibrational measurements as well as rotational or electronic studies and nonlinear effects. Following, Raman will be used in the established but slightly inaccurate way as a synonym for the most important and most common technique of the family, linear vibrational Raman scattering. 

In order to realize molecular-vibration spectroscopy, coherent anti-Stokes Raman scattering (CARS) spectroscopy is employed, which is one of the most widely used nonlinear Raman spectroscopes (Shen 1984). CARS spectroscopy uses three incident fields including a pump field (< i), a Stokes field (0)2, 0 2 < 1) and a probe field (<0/ = <0i), and induces a nonlinear polarization at the frequency of <03 = 2<0i - <02 which is given in a scalar form by... 

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