Spectrum beam-foil

Fig.6.4. Example of a beam-foil spectrum obtained using an accelerated iron-ion beam [6.29]...

The monochromatic X-ray was obtained by silicon (111) channel cut double crystal using white X-ray (at Beam Line 4A (PF)). The ion chambers were set at the both side of the photoacoustic cell, in order to compare the sp trum of photoacoustic X-ray absorption spectroscopy (PAXAS) with usual absorption spectrum, simultaneously. The chopper at chopping frequency of 10 Hz was t at the up-stream of these detectors. Copper foil (5 pm thick) was used as a sample. 

When an incident beam of radiation of frequency 9 foils on a molecule, some radiation is scattered and in this scattered radiation we get, as well as r, frequencies where is a fundamental frequency. This is called the Baman effect and when a fundamental frequency appears in the Baman spectrum it is said to be Baman active. 

Schematically, the studies proceed as follows the white synchroton radiation beam is at the same time focused and dispersed in energy by a curved crystal. The sample is located at the focus point, and the detection is done by a positon-sensitive detector, such as a photodiode array, that is able to withstand a very high photon flux. Therefore, the relationship Bragg angle-energy of the diffracted beams is translated into a correlation energy-position in the detector. In the best cases, like an elemental copper foil, only a few milliseconds are needed to acquire an EXAFS spectrum.

The first prerequisite for measurement of photoelectron spin-polarization is the ability to separately detect the photoelectrons ejected from the different fine-structure levels (e.g., 2n3/2 and 2n1/2 for HX+ X2n). When the molecule contains a heavy atom (e.g., large spin-orbit splitting), it becomes easier to use the electron kinetic energy to distinguish the photoelectrons ejected from the different fine structure channels. For spin-polarization analysis, the accelerated electron beam (20-120 keV) can be scattered by a thin gold foil in a Mott-detector. The spin-polarization is determined from the left-right (or up-down) asymmetry in the intensities of the scattered electrons (Heinzmann, 1978). Spin polarization experiments, however, are difficult because the differential spin-up/spin-down flux of photoelectrons is typically one thousandth that obtained when recording a total photoionization spectrum. 

Deuteron capture using the Fe(iron foil produces the normal Fe metal spectrum [52], as does a 4-8-MeV pulsed beam of deuterons with a stainless steel target [53]. 

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