Coherent anti-Stokes Raman scattering CARS

The present study demonstrates that the analytic calculation of hyperpolarizability dispersion coefficients provides an efficient alternative to the pointwise calculation of dispersion curves. The dispersion coefficients provide additional insight into non-linear optical properties and are transferable between the various optical processes, also to processes not investigated here as for example the ac-Kerr effect or coherent anti-Stokes Raman scattering (CARS), which depend on two independent laser frequencies and would be expensive to study with calculations ex-plictly frequency-dependent calculations. 

Coherency strains, 13 501 Coherent anti-Stokes Raman scattering (CARS), 21 328 Cohesive energy, 23 90 Coho salmon, common and scientific names, 3 187t... 

Legare, F., Ganikhanov, F., and Xie, X. S. 2005. Towards an integrated coherent anti-Stokes Raman scattering (CARS) microscope system. Proc. SPIE 5971 35 0. 

Pastirk, I., DelaCruz, J. M., Walowicz, K. A., Lozovoy, V. V., andDantus, M. 2003. Selective two-photon microscopy with shaped femtosecond pulses. Opt. Exp. 11(14) 1695-1701. Potma, E. O., Evans, C. L., and Xie, X. S. 2006. Heterodyne coherent anti-Stokes Raman scattering (CARS) imaging. Opt. Lett. 31(2) 241M 3. 

Lim, S. H., Caster, A., and Leone, S. R. 2005. Single pulse phase-control interferometric coherent anti-Stokes Raman scattering (CARS) spectroscopy. Phys. Rev. A 72 041803. 

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... 

Before melting and for some time after only the band at 625 cm of the AA [C4CiIm]+ cation was observed in the 600-630 cm i region. Gradually 603 cm i band due to the GA conformer became stronger. After about 10 min the AA/GA intensity ratio became constant. The interpretation [50] is that the rotational isomers do not interconvert momentarily at the molecular level. Most probably it involves a conversion of a larger local structure as a whole. The existence of such local structures of different rotamers has been found by optical heterodyne-detected Raman-induced Kerr-effect spectroscopy (OHD-RIKES) [82], Coherent anti-Stokes Raman scattering (CARS) [83],... 

Coherent anti-Stokes Raman scattering (CARS) spectra of O2 (15) and H2 (16) have been recently obtained. This opens up a very important class of molecules to direct detection. It is now possible, with the right parent molecule, to study the dynamics of the molecular detachment process. It will be particularly interesting to see the dynamical results that will be obtained in the future on the VUV photodissociation of hydrocarbons, such as the. vibrational and rotational excitation of the H2 product. 

Coherent anti-Stokes Raman scattering (CARS) microscopy is an emerging technology. By tuning a pump laser and a Stokes laser to a Raman-active molecular vibration, molecular selectivity and faster measurement speed can be obtained. This approach has been used to track the phase segregation, crystallisation and dissolution of paclitaxel from biocompatible excipients and films providing kinetic data not achievable through standard Raman microscopy methods [56]. 

In exemplarily flame measurements conducted at the LTT-Erlangen (Will et al., 1996), flame temperatures were determined by emission spectroscopy or coherent anti-Stokes Raman scattering (CARS) thermometry depending on the maximum soot concentration. Typical temperatures are in the range of 1800 K in the middle of the flames and up to 2100 K in the outer regions where the reactions take place. A typical measurement setup for two-dimensional LII investigations is shown in Figure 10. 

A CCD Raman spectrometer coupled with a 10-mW He-Ne laser has been used to eliminate fluorescence because the long-wavelength excitation by the He-Ne laser is not as likely to cause fluorescent transitions (71). Because of its directional property, coherent anti-Stokes Raman scattering (CARS) is also effective in avoiding fluorescence interference (see CARS in Section 3.9). 

Here, E is the strength of the applied electric field (laser beam), a the polarizability and / and y the first and second hyper-polarizabilities, respectively. In the case of conventional Raman spectroscopy with CW lasers (E, 104 V cm-1), the contributions of the / and y terms to P are insignificant since a fi y. Their contributions become significant, however, when the sample is irradiated with extremely strong laser pulses ( 109 V cm-1) created by Q-switched ruby or Nd-YAG lasers (10-100 MW peak power). These giant pulses lead to novel spectroscopic phenomena such as the hyper-Raman effect, stimulated Raman effect, inverse Raman effect, coherent anti-Stokes Raman scattering (CARS), and photoacoustic Raman spectroscopy (PARS). Figure 3-40 shows transition schemes involved in each type of nonlinear Raman spectroscopy. (See Refs. 104-110.)... 

Coherent anti-Stokes Raman scattering (CARS) [28]... 

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. 

Coherent Anti-Stokes Raman Scattering (CARS). In addition to the nonpara-metric SRS process to generate Stokes-shifted beams that propagate collinearly with the vq pump radiation, a second parametric process can occur that generates noncollinear beams at frequencies Vsi = vq + I yand vsi = vq - Vj. The energy level diagram for... 

Periodic oscillations in this dipole can act as a source term in the generation of new optical frequencies. Here a is the linear polarizability discussed in Exps. 29 and 35 on dipole moments and Raman spectra, while fi and x are the second- and third-order dielectric susceptibilities, respectively. The quantity fi is also called the hyperpolarizability and is the material property responsible for second-harmonic generation. Note that, since E cos cot, the S term can be expressed as -j(l + cos 2 wt). The next higher nonlinear term x is especially important in generating sum and difference frequencies when more than one laser frequency is incident on the sample. In the case of coherent anti-Stokes Raman scattering (CARS), X gives useful information about vibrational and rotational transitions in molecules. 

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