Impulsive stimulated Raman scattering

The classical equation of motion1 describing the coherent phonons for a small nuclear displacement Q is that of a driven harmonic oscillator [9,10,15] 

Up to now, only Raman active modes at the r point of the Brillouin zone have been observed as coherent phonons in bulk crystals.2 The selection rule can be 

2 Exceptions include coherent IR-active (but Raman-inactive) phonons observed as 

The key requirements for ISRS excitation are the existence of Raman active phonons in the crystal, and the pulse duration shorter than the phonon period loq1 [19]. The resulting nuclear oscillation follows a sine function of time (i.e., minimum amplitude at t=0), as shown in Fig. 2.2e. ISRS occurs both under nonresonant and resonant excitations. As the Raman scattering cross section is enhanced under resonant excitation, so is the amplitude of the ISRS-generated coherent phonons. 

Experimental verification of the ISRS generation can be primarily given by the pump polarization dependence. The coherent phonons driven by ISRS (second order process) should follow the symmetry of the Raman tensor, while those mediated by photoexcited carriers should obey the polarization dependence of the optical absorption (first order process). It is possible, however, that both ISRS and carrier-mediated generations contribute to the generation of a single phonon mode. The polarization dependence is then described by the sum of the first- and second-order processes [20-22], as shown in Fig. 2.3. 

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Yan Y X, Gamble E B and Nelson K A 1985 Impulsive stimulated Raman scattering general importance in femtosecond laser pulse interactions with matter, and spectroscopic applications J. Chem. Phys. 83 5391-9... 

Walsh A M and Loring R F 1989 Theory of resonant and nonresonant impulsive stimulated Raman scattering Chem. Phys. Lett. 160 299-304... 

A light pulse of a center frequency Q impinges on an interface. Raman-active modes of nuclear motion are coherently excited via impulsive stimulated Raman scattering, when the time width of the pulse is shorter than the period of the vibration. The ultrashort light pulse has a finite frequency width related to the Fourier transformation of the time width, according to the energy-time uncertainty relation. 

Fig. 2.2. Two generation models of coherent optical phonons, (a), (c), (e) impulsive stimulated Raman scattering (ISRS). (b), (d), (f) displacive excitation of coherent phonons (DECP). Graphs (e) and (f) display the time evolution of the driving force (grey areas) and that of the displacement (solid, curves) for ISRS and DECP, respectively...

D. M. Neumark We are interested in generating coherent vibrational motion in negative ions, which typically do not have bound excited electronic states. Does your Impulsive Stimulated Raman Scattering (ISRS) scheme work if the excited state is not bound ... 

Dougherty TP, Wiederrecht GP, Nelson KA. Impulsive stimulated Raman scattering experiments in the polariton regime. J Opti Soc Am B 1992 9(12) p. 2179. 

Impulsive stimulated Raman scattering (ISRS) Impulsive stimulated Raman scattering (ISRS) is the creation of coherent ground-state nuclear motion through an impulsive force caused by the interaction of a Raman-active medium with an ultrashort light pulse. 

When a femtosecond laser pulse passes through nearly any medium, coherent vibrational excitation (in general, initiation of coherent wavepacket propagation) is likely [33, 34]. One- or two-photon absorption of a visible or ultraviolet pulse into an electronic excited state can result in phase-coherent motion in the excited-state potential [35]. Impulsive stimulated Raman scattering can initiate phase-coherent vibrational motion in the electronic... 

Impulsive stimulated Raman scattering (ISRS) signal shows oscillations at twice the vibrational frequency and decay at twice the vibrational dephasing rate. 

Chesnoy, J. and Mokhtari, A. (1988) Resonant impulsive-stimulated Raman-scattering on Malachite Green. Phys. 

S. Ruhman, A.G. Joly, and K.A. Nelson, Coherent Molecular Vibrational Motion Observed in the Time Domain Through Impulsive Stimulated Raman Scattering , IEEE J. Quant. Electr. 24, 460 (1988). 

J. Chesnoy and A. Mokhtari, Resonant Impulsive-Stimulated Raman Scattering on Malachite Green , Phys. Rev. A 38, 3566 (1988). 

LA. Wamsley, F.W. Wise, and C.L. Tang, On the Difference between Quantum Beats in Impulsive Stimulated Raman Scattering and Resonance Raman Scattering , Chem. Phys. Lett. 154, 315 (1989). 

R. Kosloff, A.D. Hammerich, and D.J. Tannor, Excitation without Demolition Radiative Excitation of Ground Surface Vibration by Impulsive Stimulated Raman Scattering with Damage Control , Phys. Rev. Lett. 61, 2172 (1992). 

Ruhman, S., Joly, A.G. and Nelson, K.A. (1988). Coherent molecular vibrational motion observed in the time-domain through impulsive stimulated Raman scattering. IEEE J. Quantum Electron. QE-24 460 69. 

Chang, Y.J., Cong, P. and Simon, J.D. (1995). Optical heterodyne detection of impulsive stimulated Raman scattering in liquids. J. Phys. Chem. 

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