Calibration full energy peak

In this experiment, the Ge detector with spectrometer is calibrated for its efficiency, s, with a standard that emits a set of gamma rays at energies that span the range of interest, usually from a few keV to 1.5 MeV. The counting efficiency is calculated from the ratio of the net count rate to the reported disintegration rate at each full-energy peak in the spectrum. A correction for radioactive decay is needed. 

Carefully swirl to mix. Be certain to cover the bottom evenly, but do not swirl the solution up onto the container walls. The total initial volume is 5.0 mL. Screw the lid on the container and carefully place in position in the germanium gamma-ray detector counting chamber it should be centered and level. Count twice for a sufficient time period to accumulate 2000 counts (typically 100 s). Check to confirm that at least 2,000 counts have been accumulated at each of the peaks used for calibration. Collect the gross gamma-ray count rates for the full-energy peaks in Data Table 2B.1. 

Apart from keeping a record of the state of the equipment, the routine calibration parameters should be monitored by means of control charts. One might monitor, for example, the resolution at two energies, the energy calibration factors, and the full-energy peak efficiency at two energies. A simple example is shown in Figure 15.2. 

Having constructed energy, peak width and efficiency calibration curves, the way is clear to performing a full... 

Figure 5 shows the results for model T. The calculated spectra were obtained from Gaussian convolution applied to the election transition probabilities Irom the Ni Is orbital with a full-width at half-height (FWHH) of 1.0 eV. The energy scale for the ceilculated spectra was calibrated by assigning the calculated Is —> 3d transition to the energy of the pre-edge peak in the each recorded XANES spectra. The calculated spectra have three peaks, which however, have a poor fit to the observed one at the positions arrowed, especially, the point II. 

II. c XPS spectra were recorded using a SSI-X probe (SSX-100-206) spectrometer of FISONS with monochromatised AIK, radiation.The spectrometer energy scale was calibrated using the Au 4f7/2 peak ( binding energy 93.98 eV). With the analyzer resolution used (50 eV) for rea>rding individual peaks the full v th at half maximum of Au 4f7/2 peak was of 1.0 eV. 

If a spectrometry system is used in simple fashion with peak areas derived from manually set regions-of-interest, there is no need for a peak width calibration. However, if the computer is used in any way in a calibration or analysis then it becomes necessary to tell the computer what the shape of a peak is. I will discuss this in more detail in Chapter 9 but in simple terms, the computer needs to be able to deduce the width (by convention, the full width at half maximum, FWHM) of a peak as a function of energy. 

The system can then search for the required peaks, find their centroids and fit an appropriate function to the pairs of position/energy data. In most cases, the choice of appropriate function will be determined by the system itself. A hardwired analyser is unlikely to allow more than a two point calibration. Even in an MCA emulator system such as Maestro-II, users are limited to a two point linear calibration. Using the companion full spectrum analysis program, GammaVision, this initial calibration can be replaced by a multi-point calibration fitted to a quadratic equation ... 

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