Acceptance angle

Foi shts placed at from the center of curvature, the electrons passed by this analyzer foUow the equipotential surface described by R. With an acceptance angle 8a shown in Figure 22 and a sht width w, the energy resolution of the CFIA is given by... 

The curve labeled geometry illustrates the kinematic energy spread due to the finite acceptance angle of the detector. The multiple scattering contribution arises from the spread in ion energies introduced by secondaiy scattering events. 

If the angular spread of the acceptance angle is Aa, the relative energy resolution of a CMA is ... 

Elastic collisions and chemical reactions in the sheath lead to a broad angular distribution of the ion velocity at the electrode. Examples for SiH and SiH are the abstraction reactions SiH -I- SiH4 SiH4 -f- SiH [330] and SiH - -SiH4 —> SiH + SiH3 [331], Due to the small acceptance angle of the EQP, these processes are only in part reflected in the lED [163, 332]. 

In order to study the influence of ions on the deposition process, a reliable quantification of the ion flux and energy is imperative. This flux cannot be determined directly from the detected number of ions in an lED as measured by means of QMS, for three reasons [332]. First, the orifice size decreases during subsequent measurements due to deposition of a-Si H on the edges of the orifice. Second, due to the limited acceptance angle of the mass spectrometer system, only a fraction of the ions that arrive at the substrate is actually detected. This fraction depends on the type and number of interactions that an ion experiences while traversing... 

Figure 5.38. Illustrating the incident electron beam convergence angle (a), the scattering angle (6) and the spectrometer acceptance angle (/l) in electron energy loss spectroscopy. (After Joy, 1981.)...

In order to allow for back scattering and plasmon scattering in the sample to be evaluated directly from the spectrum, / in equation (4) is conventionally replaced by /0((3A), the integral in the energy window under the zero-loss peak, for the acceptance angle (3. This permits the calculation of the absolute number of atoms which contributed to the edge. 

If measurements are made in thin oxide films (of thickness less than 5 nm), at highly polished Al, within a small acceptance angle (a < 5°), well-defined additional maxima and minima in excitation (PL) and emission (PL and EL) spectra appear.322 This structure has been explained as a result of interference between monochromatic electromagnetic waves passing directly through the oxide film and EM waves reflected from the Al surface. In a series of papers,318-320 this effect has been explored as a means for precise determination of anodic oxide film thickness (or growth rate), refractive index, porosity, mean range of electron avalanches, transport numbers, etc. 

To obtain the measured intensity, one needs to correct (3-15) and (3-16) for the transmission and the acceptance angle of the detector. 

Lower limit of acceptability for scattering peak (degrees 20) Accepted angle for scattering peak (degrees 20) Upper limit of acceptability for scattering peak (degrees 20)... 

Numerical aperture is thus a quantitative measure of the "acceptance" angle of a lens. Likewise the numerical aperture of the condenser lens in Figure 16 is defined as... 

The second method uses pulsed lasers and the laser-induced fluorescence is detected by telescope. If the telescope and the laser source have a definite base distance, the crossing of laser beam and the acceptance angle of the telescope define the height of the atmospheric layer at which fluorescence is detected. There is also the technique of delayed coincidence, where the time interval between laser pulse and detected fluorescence pulse determines the distance of the observed molecules from the observer (Lidar)... 

The maximum input acceptance angle for a fiber-optic cable is determined by the critical angle for total internal reflection, which is given by Snell s law ... 

Figure 5.30 Internal reflection and acceptance angle in a fiber-optic cable.

Plots of each of these quantities as a function of particle size would look quite different and, therefore, would tell different stories. Except for a scale factor, each of them plotted as a function of wavelength for the same particle size would be identical. In our first example of extinction (Fig. 4.6) we displayed the efficiency Qext, as we shall often do in this chapter. In Chapter 12, however, our preference switches to the extinction cross section per unit particle volume. Unnormalized extinction cross sections (strictly speaking, the differential scattering cross section integrated over the acceptance angle of the detector) are more appropriate in Section 13.5 on particle sizing. 

Fig. 1. Types of linear (a) and pen linear (b) and (e) hydrogen bonds (diagrammatic only). In (b) the hydrogen atom points nearly in the direction of the centre of the acceptor atom but the electron pair does not point to the donor atom making an appreciable acceptance angle.

In these cases, a variation of the distance between the sample and the detector, in which the variation of the detector acceptance angle is also examined, provides an easier diagnosis on the distortion of the CD resulting from the linear birefringence, linear dichroism, and light-scattering effects. 

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