Monochromator plane mirror

Electrothermal atomizers are also suitable for AFS as, when an inert gas atmosphere is used, quenching will be minimized. In the nuclear, electronic, semiconductor and biomedical industries where detection limits have to be pushed as low as 1 part in lO (or 0.1 pg g- in the original sample), electrothermal atomization with a laser as excitation source (LIF-ETA) may be used. Figure 6.5 shows schematically a common way of observing the fluorescence in LIF-ETA. The fluorescence signal can be efficiently collected by the combination of a plane mirror, with a hole at its centre to allow excitation by the laser, positioned at 45° with respect to the longitudinal axis of the tube and a lens chosen to focus the central part of the tube into the entrance slit of the fluorescence monochromator. 

Most available infrared instruments use the Littrow mount for the prism, the beam being reflected from a plane mirror behind the pnsm and thus returning it through the prism a second time. This doubles the dispersion produced. Actually, a double-pass system is also used so that the beam goes through the pnsm four times. Other design modifications include those with single beam and double monochromator, double beam and double monochromator, and related combinations, See also Infrared Radiation. 

Fig. 4.1. Schematic of an experimental set-up for absorption measurements at low temperature incorporating a Perkin-Elmer Model 99G monochromator. Si, S2 and S3 are IR sources selectable with plane mirrors Mi and M2. FM focusing spherical mirrors. Ei and E2 entrance and exit slits. CM off-axis paraboloid collimating mirror. G plane reflection grating. Beam 1 from Si is converted by CM into a parallel beam dispersed by G. One wavelength is diffracted in a direction where it can be intercepted by first mirror M as beam 2 and focused on the internal chopper Ch. Modulated beam 2 is redirected toward G as beam 3 and re-dispersed a second time as beam 4. Beam 4 intercepted by IM is focused on E2 and re-focused on the sample by FM. The divergent monochromatic beam is finally focused on thermocouple D by ellipsoidal mirror EFM. Fi, F2 and Pol are locations for transmission filters and a polarizer. Beam 1 can be blocked by shutter Sh (after [37]). With permission from the Institute of Physics...

The diverged infrared radiation from the input slit is directed to a parabolic mirror and returned toward the splitting system (prism or gird). Depending on the type of optical principle, the parallel reflected infrared light passes through the prism or split by the diffraction gird. It is then reflected back by a plane mirror at the same parabolic reflector for the Littrow monochromator or at a second parabolic reflector for the Ebert monochromator. After this, the monochromic infrared radiation is directed to the output slit. 

Fig. 2.4 Geometrical arrangement of a plane mirror monochromator for circularly polarized light in the soft X-ray region...

Monochromators employing prisms for dispersion use a Littrow 60° prism plane mirror mount. Midinfrared instruments employ a sodium ehloride prism for the region from 4000-650 cm (2.5-15.4 pm), a potassium bromide or cesium iodide prism and optics extend the useful speetrum to 400 em (25 pm) or 270 em (37 pm), respectively. Quartz monochromators, designed for the ultraviolet visible region, extend their eoverage into the near infrared to 2500 cm (4 pm). 

Fig. 8. The planned instrument for resonance scattering in the normal and soft X-ray spectrum of synchrotron radiation. It is presently under construction and will be installed at the beam line A1 of HASYLAB. The beam path is kept constant till the crystal monochromator. The camera is rotated by 2 0 in the vertical plane in order to follow the 0 movement of the monochromator crystal, during an energy scan. The camera is evacuated. There is only a very thin window between the second mirror and the monochromator...

Fig. 2 a. Focusing geometry of a SAXS-camera [11, 32]. b. Schematic design of a focussing SAXS-camera with a pinhole geometry. S, and S2 are the aperture and guard slits. The optical element could be a mirror or a monochromator, m corresponds to the — idealized — extension of the diffuse scattering in the detector plane. as is the size of the source point and and a that of the focus. Note that the calculations of SAXS-resolution assume that F2 L, + L2... 

The X-ray mirror on the camera consisted of two 20 cm segments of fused quartz each of which had a separate bending mechanism. The monochromator was either a bent quartz crystal (101 plane) or Ge (111), each with an oblique cut of 7° the crystals were rectangular with equal couples applied at each end to obtain the necessary curvature (same principle as the mirror bender). 

The beam line optics consists of a bent Si (111) monochromator. Various crystals with different oblique-cut angles are available, namely a=0°, 6.0°, 7.8°, 9.5°, 11.4°, 13.7° and 16.5° to allow an energy range of 5-25 keV to be covered, by appropriate choice of crystal. There is a bent plane fused quartz mirror (Satow, Mikuni, Kamiya and Ando 1989). 

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