Transmitted intensity

A RIKES experunent is essentially identical to that of CW CARS, except the probe laser need not be tunable. The probe beam is linearly polarized at 0° (—>), while the polarization of the tunable pump beam is controlled by a linear polarizer and a quarter waveplate. The pump and probe beams, whose frequency difference must match the Raman frequency, are overlapped in the sample (just as in CARS). The strong pump beam propagating tlirough a nonlinear medium induces an anisotropic change in the refractive mdices seen by tlie weaker probe wave, which alters the polarization of a probe beam [96]. The signal field is polarized orthogonally to the probe laser and any altered polarization may be detected as an increase in intensity transmitted tlirough a crossed polarizer. When the pump beam is Imearly polarized at 45° y), contributions... 

Amorphous orientation average Crystalline orientation average Nuclear spin number Scattered intensity Scattered intensity Transmitted intensity... 

The intensity transmitted to the waveguide can be related to the Poynting vector of the incident ffee-space radiation and that of the PhC-mode a few microns away from the interface, which confirms the 80% coupling efficieny. 

Detectors for quantitative measurement of X-ray absorption spectra must measure the flux (photons s of the X-ray beam. Ionization chambers consisting of X-ray transparent windows on each end of a chamber holding an inert gas work well as transmission detectors for concentrated samples. For transmission detectors, ln(/o//) is proportional to the absorption coefficient of the absorbing atom, p (/o = incident X-ray photon intensity, /= transmitted intensity), according to Beer s Law ... 

Figure 5.4 provides a schematic diagram of a Mossbauer experiment in transmission mode with a moving single-line source and the absorbing sample in fixed position. A Mossbauer spectrum is a plot of the y-ray intensity transmitted by the sample, against the velocity v of the source. The latter is related to the... 

There are materials, for example in the form of certain specially prepared polymer films, which, for light incident normal to the film, absorb to an extent dependent on the inclination of the plane of polarization to a unique axis in the plane of the film. Devices made from such films are termed polarizers approximately 60% of the incident unpolarized light is absorbed, and that part transmitted is plane polarized. The E vectors for the transmitted light are perpendicular to the high-absorbance direction. If the incident light is plane polarized, the intensity transmitted depends on the orientation of the polarizer axis with respect to the plane of polarization of the light. A device used in this mode is usually referred to as an analyser . 

An expression is now derived for the light intensity transmitted by P2 in the case where the relative retardation introduced by the specimen is T and the compensator is removed. It is helpful to refer to Fig. 8.10(b) which represents the system viewed from the photodiode. If the amplitude transmitted by the polarizer P, is a sin(cot), then the. v and y components incident on the PLZT are... 

The line broadening due to light-shift and saturation is shown in Fig.4 where the experimental linewidth of the 2Si/z - 10Bo/z transition in deuterium is reported versus the light intensity transmitted through the excitation cavity. 

In transmission spectroscopy, the light intensity transmitted through the sample is either simultaneously or consecutively compared with that transmitted by a reference, which is considered as 100% transmittance (Iq)- The reference spectrum can either be obtained with an... 

An EXAFS spectrum is a plot of the X-ray intensity transmitted by the sample, as a function of the energy E = fiv of the monochromatic X-rays. Each time E reaches the threshold for photoemission of a core electron with binding energy... 

We now consider the radiative decay of the excited ensemble of atoms. The angular distribution and polarisation of the emitted photons can be conveniently described in terms of the Stokes parameters I, t]i, t]2, and (Born and Wolf, 1970). The emitted photons can be observed in the direction n making polar angles 6 and azimuthal angles with respect to the collision frame (fig. 8.1). It is convenient to choose the coordinate system in which the direction of observation n of the radiation is chosen as the z axis. The polarisation vector of the photons is restricted to the plane perpendicular to n by the two unit vectors i = (0 + 90°, 0) and 2 = (0,light emitted in the direction n and I y) the intensity transmitted by a linear polariser oriented at an angle y with respect to the i-axis, then the Stokes parameters are defined by... 

The most simple dispersive spectrometer (Fig. 12.2) comprises a source, a monochromator and a detector. The monochromator, made up of an entrance slit, an output slit and prisms or gratings, is u,sed to separate the light into its basic components. The role of the slit system is to enhance the spectral resolution and compensate for intensity variations. The transmission infrared spectrum of the sample is the recording of the light intensity transmitted as a function of the wave-numbers w hich are scanned in front of the monochromator output slit by rotating the dispersive element. In the infrared domain, the wave-numbers are always recorded sequentially, due to the single-channel nature of the detectors. This recording is compared to that of the reference or the source in order to deduce the absorption due to the sample. 

UV intensity transmitted by the sample at the desired UV wavelength, mW/cm Average intensity of UV light, mW/cm ... 

We have now recognized two ways in which the intensity transmitted by a given domain between crossed polars is affected by adjacent material ... 

If a beam of polarized radiation is passed through a linear polarizing filter, the intensity transmitted is a function of the angle between the filter polarization axis and the polarization direction of the beam. When the angle is zero, all radiation is transmitted (for an ideal filter there are always losses by reflection, background absorption, etc) when the angle is 90°, all radiation is blocked (absorbed) by the filter. 

For intermediate angles, the fraction of intensity transmitted is given by the square of the co-sine of the angle (Malus law). This is easily understood as the electric field vector can be decomposed in two orthogonal components, one along the polarization axis that is transmitted, and one along the perpendicular direction that is absorbed. Since intensity is proportional to the square of the electric field amplitude, the Malus law follows. 

CDOM is usually described in terms of its absorbance over the environmentally relevant wavelength range of 280 to 700 nm, encompassing the UV and the visible portions of the solar spectrum. Absorbance, measured by a spectrophotometer, is the log base 10 ratio of the light intensity, 1q, incident on the sample to the light intensity, /, transmitted by the system ... 

Light intensities transmitted in the absence of the analyte Light intensities transmitted in the presence of the analyte Absorption coefficient Optical path length... 

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