Monochromators double crystal type

Figure 3 shows one of our photoacoustic cell for X-ray spectroscopy of solid samples The cylindrical cell has a sample chamber at the center with volume of 0.16 cm which has two windows of beryllium (18 mm x 0.5 mm thickness). A microphone cartridge is commercially available electret type (10 mm ) and the electronics of preamplifier for this microphone is detailed elsewhere Figure 4 shows the typical experimental setup for spectroscopic study X-ray was monochromated by channel cut silicon double crystal (111) and ion chamber was set to monitor the beam intensity. Photoacoustic signal intensity was always divided by the ion chamber current for the normalization against the photon flux. X-ray was modulated by a rotating lead plate (1 mm thick) chopper with two blades. 

Most of the L spectra, measured during the early period of X-ray spectroscopy were recorded with energy dispersive spectrometers on photographic films. In many respects the gross spectral features recorded with this type of spectrometers match those recorded with today s state-of-the-art spectrometers. Large chemical shifts can be traced from such data, e.g., the significant shifts of about 8eV in the L, spectra of lanthanide materials with different valence states. Accurate measurements of amplitudes and lineshapes, however, are best performed with modem double crystal monochromators and with the use of synchrotron radiation (cf. section 5). 

An early type of this double monochromator is used with the instrument X15 at EMBL, Hamburg ( This consists of two separate single crystals. The first crystal... 

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