Diverging beam

The foremost of the modem teclmiques is tlie use of lasers as spectroscopic tools. Lasers are extremely versatile light sources. They can be designed with many usetlil properties (not all in the same instmment) such as high intensity, narrow frequency bandwidth with high-frequency stability, tunability over reasonable frequency ranges, low-divergence beams which can be focused into very small spots, or pulsed beams with... 

The hexapole cannot act as a mass filter by applying a DC field and is used only in its all-RF mode, in which it allows all ions in a beam to pass through, whatever their m/z values. In doing so, the ion beam is constrained, so it leaves the hexapole as a narrow beam. This constraint is important because the ion beam from the inlet system tends to spread due to mutual ion repulsion and collision with residual air and solvent molecules. By injecting this divergent beam into a hexapole unit, it can be refocused. At the same time, vacuum pumps reduce the background pressure to about 10 mbar (Figure 22.1). The pressure needed in the TOF analyzer is about 10 ... 

Fig. 4-7. Diffraction of a divergent beam from a broad sample by a large crystal. Collimation of this beam requires the Soller slit system shown. This system is equivalent to simple slits at A and B with separators provided to make certain that only parallel rays leave the exit slit.

As Sherman15 points out, the enhancement components are generated within the sample and radiated with spherical symmetry, so that it is necessary to integrate at every point over the entire solid angle in order to obtain their intensities. In other words, one must deal here with broad, divergent beams,16,17 and this leads to integrands of the form [log (a + bx)]/x, which are more difficult to handle than the simple exponential integrand that underlies Equation 6-5. 

The output divergent beams overlap with each other and the final interference pattern is a superposition of individual interference patterns, each of them representing the overlap of the divergent beams of a specific channel pair. The interference pattern is recorded by a CCD camera, which is placed at a distance L from the chip endface. The irradiance distribution of the sum interference pattern at the input face of the camera can be derived to be32... 

Monochromatic laser light of an Ar+ laser (Innova 70 Spectrum Coherent, Inc., Santa Clara, CA) with a wavelength of 647 nm is end-fire coupled into the input fiber connected to the YI chip. The four output divergent beams overlap one another on the front side of a CCD camera (Teli CS-3440 756 x 575 pixels, vvPjxei =11.6... 

Fig. 4.18. Direction focusing properties of a 180° magnetic sector on a diverging beam of ions of the same m/z and the same kinetic energy and effect on ions of different m/z- In this illustration, B has to come out of the plane towards the reader for positive ions.

When a strongly divergent beam is used to illuminate the particle, it is possible to generate a negative light pressure which can be used to trap a particle. This phenomenon was discovered by Ashkin et al. (1986), and it is illustrated in Fig. 17. In this case rays A and A, which we assume are of equal... 

Among the first practical applications, research studies have been interested to fathom possible potentials and limitations of LAPS-based measurements. One distinguishing feature of the LAPS is its spatial resolution. The resolution of a LAPS system is limited by several factors such as the definition of the light source (e.g., wavelength, beam diameter, beam divergence, beam intensity, etc.) and the LAPS geometry of the build-up (layer scheme, layer thickness, material properties,... 

FIGURE 6.3 Absorption of light of a highly divergent beam by a substance placed in a cylindrical cell. Although the effect of reflection on the window has not been considered here, it can be introduced by a simple application of the laws of geometrical optics. 

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