A Review of the Theory and Application of Coherent Anti-Stokes Raman Spectroscopy (CARS)

Abstract

Coherent anti-Stokes Raman spectroscopy (CARS) is a relatively new kind of Raman spectroscopy which is based on a nonlinear conversion of two laser beams into a coherent, laser-like Raman beam of high intensity in the anti-Stokes region. The emission is often many orders of magnitude greater than normal Raman scattering and, because of the coherent and anti-Stokes character of radiation, the method is very useful for obtaining Raman spectra of fluorescing samples, gases in discharges, plasmas, combustion, atmospheric chemistry. In this paper we outline the basic theory behind CARS and describe its unusual effects and drawbacks. We review the research to date on various materials, and indicate the possible future direction, utility and applications of CARS such as surface studies, fluctuation phenomena, reaction dynamics, photochemistry, kinetics, relaxation, and energy transfer.

Review of temperature measurement

“…155 CARS permits noninvasive local temperature measurement in gases, flames, or plasmas. 156 Since temperature is related to the rotational state of the molecules, the anti-Stokes lines increase in intensity with increasing temperature. This is caused by photon-molecule collisions in which the incoming photon captures some rotational energy from the molecule and arrives at the detector with higher energy and hence higher frequency.…”

Possibilities and limitations of off-resonance polarization sensitive cars of short chain proteins

“…Besides this pR dependence, the intensity of the lorentzian spectral bands in the PCARS spectra depends quadratically on the Raman scattering crosssection. This is in contrast with the dispersive interference with the nonresonant background in normal CARS, which results in a linear relationship [ 7 ]. Spectral contributions with a small scattering crosssection and/or a depolarization ratio close to pNR, are therefore more easily detected when a controlled amount of nonresonant signal is mixed with the vibration resonant signal.…”

Automated Motile Cell Capture and Analysis with Optical Traps

“…based on coherent anti-Stokes Raman scattering in which three electric fields: the pump, Stokes, and probe interact with molecules in a sample to generate the antiStokes signal (Cheng and Xie, 2004;Duncan et al, 1982;Tolles et al, 1977). Molecular specificity is achieved from characteristic molecular vibrations of endogenous species.…”