Nestor J, Spiro T G, Klauminzer G
Proc Natl Acad Sci U S A. 1976 Oct;73(10):3329-32. doi: 10.1073/pnas.73.10.3329.
Coherent anti-Stokes Raman scattering (CARS) spectra have been obtained for ferrocytochrome c and cyano cobalamin in aqueous solution at millimolar concentrations, using a pair of tunable dye lasers pumped by a pulsed nitrogen laser. Resonance enhancement was obtained by tuning the omega1 laser to the visible absorption bands of the samples. The spectral features correspond to those observed in the conventional resonance Raman spectra. It appears that CARS spectroscopy, with its advantageous fluorescence rejection, can be usefully applied to biological samples by exploiting resonance enhancement. While the background scattering from water is 10 times higher than that of benzene and other aromatic solvents, it is actually at the low end of the scale for most liquids. The anomalously low background of aromatic liquids is thought to result from competition by the unusually efficient stimulated Raman scattering which they display. Off-resonance spectra for both cobalamin and cytochrome c contain negative peaks, i.e., absorption bands in the background. These are interpreted as inverse Raman processes induced by the omega1 photons in the presence of the continuum provided by the background scattering. While both CARS and the inverse Raman effect are subject to resonance enhancement, the wavelength dependence of CARS is evidently steeper.
利用由脉冲氮激光器泵浦的一对可调谐染料激光器，已获得毫摩尔浓度水溶液中亚铁细胞色素c和氰钴胺素的相干反斯托克斯拉曼散射（CARS）光谱。通过将ω1激光器调谐到样品的可见吸收带获得共振增强。光谱特征与传统共振拉曼光谱中观察到的特征相对应。看来，具有有利的荧光抑制特性的CARS光谱学，通过利用共振增强，可以有效地应用于生物样品。虽然水的背景散射比苯和其他芳香族溶剂高10倍，但实际上在大多数液体的范围内处于低端。芳香族液体异常低的背景被认为是由它们所表现出的异常高效的受激拉曼散射的竞争导致的。钴胺素和细胞色素c的非共振光谱都包含负峰，即在背景中的吸收带。这些被解释为由背景散射提供的连续谱存在时ω1光子诱导的反拉曼过程。虽然CARS和反拉曼效应都受到共振增强的影响，但CARS的波长依赖性显然更陡峭。
