Time-resolved coherent anti-Stokes Raman spectroscopy

Joe T and Albrecht A C 1993 Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy of liquid benzene a Kubo relaxation function analysis J. Chem. Phys. 99 3244-51... 

Time resolved coherent anti-Stokes Raman spectroscopy of condensed matter has been recently extended to the femtosecond domain allowing direct and detailed studies of the fast relaxation processes of molecular vibrations in liquids. The vibrational phase relaxation (dephasing) is a fundamental physical process of molecular dynamics and has attracted considerable attention. Both experimental and theoretical studies have been performed to understand microscopic processes of vibrational dephasing. Developments in ultrafast coherent spectroscopy enables one now to obtain direct time-domain information on molecular vibrational dynamics. Femtosecond time-resolved coherent anti-Stokes Raman scattering measuring systems have been constructed (see Sec. 3.6.2.2.3) with an overall time resolution of less than 100 fs (10 s). Pioneering work has been per-... 

Marko, K. A., and Rimai, L. "Space and Time-Resolved Coherent Anti-Stokes Raman Spectroscopy for Combustion Diagnostics." Optic Society of America 4, no. 7 (1979) 211-13. 

NH2 radicals, generated by photolysis of NH3 (0.5 mbar) with an ArF exciplex laser at 193 nm, were detected by time-resolved, coherent anti-Stokes Raman spectroscopy in the NH stretch regions at 3334 and 3220 cm [1]. Two Raman bands of NH2, V3 = 3276 2 and V2 = 1471 2 cm were observed in solid ammonia at 77 K after irradiation with an atomic aluminium beam [2]. 

Several types of time-resolved Raman spectroscopies have been reported and reviewed by Hamaguchi and co-workers and Hamaguchi and Gustafson. These include pump-probe spontaneous and time-resolved coherent Raman spectroscopy of the anti-Stokes and Stokes varieties [coherent anti-Stokes Raman spectroscopy (CARS) and coherent Stokes Raman spectroscopy (CSRS)], respectively). Here we will focus on pump-probe time-resolved spontaneous Raman spectroscopy. 

Table II Space- and Time-Resolved Measurements from Inelastic Light Scattering. All methods are suitable for nonequilibrium conditions. Here, RS refers to Raman scattering, CARS to coherent anti-Stokes Raman spectroscopy, and RIKES to Raman-induced Kerr effect.

In this chapter we will first discuss coherent anti-Stokes Raman scattering (CARS) of simple liquids and binary mixtures for the determination of vibrational dephasing and correlation times. The time constants represent detailed information on the intermolecular interactions in the liquid phase. In the second section we consider strongly associated liquids and summarize the results of time-resolved IR spectroscopy (see, e.g., Ref. 17) on the dynamics of monomeric and associated alcohols as well as isotopic water mixtures. 

Among approaches in vibrational spectroscopy are differential and time-resolved IR and Raman spectroscopy, coherent anti-Stokes Raman scattering (CARS), Fourier transform infrared spectroscopy (FT-IR) multidimensional IR and RR spectroscopy, two-dimensional infrared echo and Raman echo [56], and ultrafast time-resolved spontaneous and coherent Raman spectroscopy the structure and dynamics of photogenerated transient spedes [50, 57]. 

Recently, the femtosecond time-resolved spectroscopy has been developed and many interesting publications can now be found in the literature. On the other hand, reports on time-resolved vibrational spectroscopy on semiconductor nanostructures, especially on quantum wires and quantum dots, are rather rare until now. This is mainly caused by the poor signal-to-noise ratio in these systems as well as by the fast decay rates of the optical phonons, which afford very fast and sensitive detection systems. Because of these difficulties, the direct detection of the temporal evolution of Raman signals by Raman spectroscopy or CARS (coherent anti-Stokes Raman scattering) [266,268,271-273] is often not used, but indirect methods, in which the vibrational dynamics can be observed as a decaying modulation of the differential transmission in pump/probe experiments or of the transient four-wave mixing (TFWM) signal are used. 

---