Stokes Raman shift

In the third stage the 708 nm light is converted to 6.02 pm via third Stokes Raman shift in a high pressure hydrogen cell. The 0.5 mJ, 7 ns long pulses are injected into a multipass cavity inside the gas target in order to effectively illuminate the muon stop region. 

Figure 1.2. Raman spectrum of room-temperature chloroform obtained with 514.5 nm light. Rayleigh scattering at zero Raman shift is heavily attenuated by a band reject filter and is actually several orders of magnitude more intense than the Raman scattering. The x axis is shown in three different scales but is normally plotted as Raman shift in reciprocal centimeters relative to the laser frequency (19,435 cm in this case). Although the Stokes Raman to the right is actually a negative frequency shift, convention assigns Stokes Raman shifts as positive numbers.

In some nonlinear wave-mixing schemes, all energy and momentum remains in the radiation field, but in others (e.g., Stokes Raman shifting, optically pumped lasers) some energy and momentum is exchanged between the radiation field and the material medium. 

Two four-wave mixing processes are briefly considered here Vacuum Ultra-Violet (VUV) generation by frequency tripling in a supersonic jet of an inert gas (Hollenstein, et al., 2000) and anti-Stokes Raman shifting in high pressure H2 gas. 

Anti-Stokes Raman shifting in high pressure H2 gas is a four-wave mixing process... 

In the experiment by Jean et al. [12], they used trans-stilben as a solute and hexane as a solvent. The temperature of the solution is kept at 295 2 K. After trans-stilben is electronically excited by a laser pulse, the intensities of the anti-Stokes Raman shifts are measured by changing the time interval after the pulse. Thus, they observed the time dependence of the vibrational energy distribution of the solute molecule. Figures 3.8 and 3.9 display their results. 

Optimal SERS enhancement therefore requires that both the incident radiation at COinc and the Stokes Raman shifted radiation at cOs = cOinc vib are in resonance with the LSPR peak of the metallic nanostructure. Generally, the nanostructures with typical dimensions 30-100 nm are necessary to fulfil the conditions of LSPR resonance with visible light. LSPR strongly depends on the size and shape of nanostructures (Schatz et al. 2006) and is also strongly modified for closely spaced... 

Bouche Th., Drier Th., Lange B., Wolfrum J., Franck E. U., Schilling W. Collisional narrowing and spectral shift in coherent anti-Stokes Raman spectra of molecular nitrogen up to 2500 bar and 700 K, Appl. Phys. B50, 527-33 (1990). 

Figure 3.17 presents ps-TR spectra of the olehnic C=C Raman band region (a) and the low wavenumber anti-Stokes and Stokes region (b) of Si-rra i-stilbene in chloroform solution obtained at selected time delays upto 100 ps. Inspection of Figure 3.17 (a) shows that the Raman bandwidths narrow and the band positions up-shift for the olehnic C=C stretch Raman band over the hrst 20-30 ps. Similarly, the ratios of the Raman intensity in the anti-Stokes and Stokes Raman bands in the low frequency region also vary noticeably in the hrst 20-30 ps. In order to better understand the time-dependent changes in the Raman band positions and anti-Stokes/Stokes intensity ratios, a least squares htting of Lorentzian band shapes to the spectral bands of interest was performed to determine the Raman band positions for the olehnic... 

Stokes number (Stk), 22 57, 23 184, 190 in depth filtration theory, 77 340 Stokes Raman scattering, 27 322 Stokes scatter, 76 485-486 Stokes shifts, 20 512 Stomach poison insecticides, 74 339... 

Figure 7.2 Complete Raman spectrum of carbon tetrachloride, illustrating the Stokes Raman portion (on left, negative shifts), Rayleigh scattering (center, 0 shift), and the anti-Stokes Raman portion (on right, positive shifts). Reprinted from Nakamoto (1997) [7] and used by permission of John Wiley Sons, Ltd., Chichester, UK.

An example of high-contrast resonant imaging of tissue structures with this source is shown in Figure 5.4a. Here, the white adipose tissue of a mouse omentum majus is imaged at a depth of -10 pm from the surface at a Raman shift of 2850 cm ( ump = 924 nm A tokes = 1254 nm). In contrast, for the same Raman shift, two synchronized Ti sapphire lasers (Potma et al. 2002) would typically have pump and Stokes wavelengths of -710 nm and -890 nm, respectively, and are much more strongly scattered in turbid tissue. 

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