Vibrational resonance Raman

Infrared and Raman spectroscopy each probe vibrational motion, but respond to a different manifestation of it. Infrared spectroscopy is sensitive to a change in the dipole moment as a function of the vibrational motion, whereas Raman spectroscopy probes the change in polarizability as the molecule undergoes vibrations. Resonance Raman spectroscopy also couples to excited electronic states, and can yield fiirtlier infomiation regarding the identity of the vibration. Raman and IR spectroscopy are often complementary, both in the type of systems tliat can be studied, as well as the infomiation obtained. 

Aramaki et al.30 examined the photochromic reactions of spirooxazines by picosecond time-resolved Raman spectroscopy. Vibrational resonance Raman spectra of the merocyanine isomer(s) recorded over a 50-ps-1.5-ns interval did not change. This indicated that the open ring opening to form a stable merocyanine isomer or the distribution of isomers31 was complete within 50 ps and that the isomer(s) distribution remained unchanged for at least 1.5 ns. 

In the adiabatic Bom-Oppenheimer approximation, the eigenstates of the unperturbed molecule, i. e. i >, / >, and r >, may be expressed as products of electronic, vibrational, and rotational states. In the following we restrict our discussion to the vibrational resonance Raman effect and hence, assuming that the molecule is initially in the vibrational state u, > and that the Raman transition starts and terminates in the ground electronic state g >, we may write... 

The occurrence of antisymmetric scattering contributions is invariably associated with processes in which the symmetry of particular electronic states becomes important. In the non-resonance electronic (or the vibro-electronic) Raman effect (ERE or VERE), the initial and final states are different electronic (or vibronic) states. Thus, if these states are of appropriate symmetry, an antisymmetric contribution may be present in the scattering 46). The same is true for the special case of the VERE represented by vibrational Raman scattering in systems possessing degenerate electronic ground states (see Section 2.11). In the resonance ERE and resonance VERE as well as the vibrational resonance-Raman effect, it is the symmetry of the intermediate state which becomes significant. 

Simplified Vertical and Adiabatic Approaches for Vibrational Resonance Raman... 

S.2.2.2 Two-Photon Absorption and Circular Dichroism The BO approximation also makes it possible to work out tractable expressions to investigate the vibrational effect for two-photon processes like, for example, vibrational resonance Raman (RR), two-photon absorption (TPA), and two-photon circular dichroism (TPCD), which are schematically depicted in Figure 8.1 along with the one-photon ones. 

S.2.2.3 Vibrational Resonance Raman Resonance Raman is a scattering phenomenon involving two photons, one incident and the other scattered. Let us consider... 

Vibrational Resonance Raman Regarding the vibrational resonance Raman, the polarizability tensor of Eq. 8.34 can also be expressed by the Taylor expansion given in Eq. 8.35 allowing us to distinguish FC and HT contributions. To simplify the equations, we will adopt a shorter notation for the derivatives of the transition dipole moment. 

It should be noted that analogous expressions depending on the general overlaps (v v) can be obtained for TPA (from Eq. 8.44), TPCD (from Eq. 8.45), and vibrational resonance Raman (from Eq. 8.46). A major issue to calculate the integrals in Eq. 8.50 arises from the fact that the vibrational wavefunctions pertaining to the two electronic states are expressed in a different set of normal coordinates. This problem can be... 

Since the transform theory adopts Eq. 8.68, it can be seen as an application of the AS model to vibrational resonance Raman, even if, as clarified below, the displacement in Eq. 8.68 can also be obtained from the VG model. 

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