Laser absorption scattering

RALLS Right-angle laser light scattering absorption spectroscopy... 

Sensitive to absorption, scatter, and sample autofluoiescence Sensitive to light lasers, photobleaching, etc. 

Chapman WB, Schiffman A, Hutson JM, Nesbitt DJ (1996) Rotationally inelastic scattering in CH4 + He, Ne, and Ar State-to-state cross sections via direct infrared laser absorption in crossed supersonic jets. J Chem Phys 105 3497-3516... 

The correction of absorption depends on the geometry of the cell and the scattering volume. Different relationships have been proposed to correct the Rayleigh factor measured with conventional goniometers, in which the detector rotates around the sample m a horizontal plane (Brice et al. 1953, Forss et al. 1967, Pla et al. 1977). With LALLS (low angle laser light scattering) pho-... 

Particle diameter Inductively coupled plasma-optical emission spectrometry (ICP-OES) Fourier transform infrared spectrometry Mass spectrometry X-ray fluorescence Extended X-ray absorption fine structure (EXAFS) spectroscopy X-ray absorption near edge (XANES) spectroscopy Static and dynamic laser light scattering Scanning probe technologies... 

Three of the experiments are completely new, and all make use of optical measurements. One involves a temperature study of the birefringence in a liquid crystal to determine the evolution of nematic order as one approaches the transition to an isotropic phase. The second uses dynamic laser light scattering from an aqueous dispersion of polystyrene spheres to determine the autocorrelation function that characterizes the size of these particles. The third is a study of the absorption and fluorescence spectra of CdSe nanocrystals (quantum dots) and involves modeling of these in terms of simple quantum mechanical concepts. 

Figure 1 - The two experimental arrangements used to probe the alignment of benzene molecules in a seeded supersonic beam by direct polarized IR laser absorption (upper device) and molecular beam scattering (lower device). For further details see Ref. [1].

Spectrophotometry Laser light scattering Optical fibers combine with absorption and fluorescence Surface plasmon resonance Photometric... 

Homogeneous assays can be performed without the need for separation. This can be advantageous with respect to convenience, time and cost of the assay and also facilitates automation. The detection method must be able to differentiate between bound and free antibodies without physically separating them from each other. An example of such a detection method is the turbidity measurement of the reaction mixture by laser light scattering or absorption. The more immuno-complexes are present in the reaction mixture, the higher its turbidity. Often, latex or gold particles are attached to the antibodies to enhance this turbidity effect. 

Finally, a spectrophotometric method has been proposed in which a low-angle laser light-scattering (LALLS) detector is used as an absorption photometer (35). Interdetector volume is then determined by injecting a solute that absorbs radiation from the LALLS detector. Mourey and Miller (35) used copper cyclohexanebutyrate as the solute and determined interdetector volume using the peak onsets of the LALLS detector and refractometer. 

Assume a short laser pulse with input power Pq is sent through an optical resonator with two highly reflecting mirrors (reflectivities R = R2 = R, and transmission T = 1 — R — A 1, where A includes all losses of the cavity from absorption, scattering, and diffraction, except those losses introduced by the absorbing sample). The pulse will be reflected back and forth between the mirrors (Fig. 6.12), while for each round-trip a small fraction will be transmitted through the end mirror and reach the detector. The transmitted power of the first output pulse is... 

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