X-Ray Fluorescence Simulation
work. The program selects unknowns by c h m i n g 1to 5 elements a t random from a list of 24 (total of 55,454 possible unknowns). These unknowns are saved on a disk file so they can be retrieved for a later session. They are automatically erased by the program if correctly determined or if the composition of the unknown is requested. The program requires determination of how many elements are in the unknown and their identity. Optionally, determination of percent composition can also be required. Either a tungsten or chromium X-ray tube can he selected by the user. There are also three choices of analyzing crystals. At least two of these must be used t o check for the presence of all possible elements. The three choices are listed helow with their 2d spacings. lithium fluoride (200 planes) 2d = 4.02 A ethylene diamine d-tartrate 2d = 8.80 A = 26.6 A potassium acid phthalate 2d Lists of the spectra (K,, La,, Lgl lines) for all 24 elements can be printed in A or degrees 20 for each crystal. Scans far the unknown. standards lsoecifv element and percentage), and tube spectra can be made in any range from
in direct proportion to it so that higher counting times give better accuracy for low percentage samples. The intensity of the X-ray line for a given percentage of an element in the sample varies from element to element. Relative intensities for the spectral series are set a t K,(150), L,1(100),L~1(50). No matrix effeck are included. It is assumed the
assumed used as needed. Answers to the quantitative analyses are counted correct if within f 10%of the true value. Some care is required in selected counting times and percent composition of standards to achieve this accuracy for unknowns in the lower percentage ranges (minimum percentage assigned to an unknown element is 5%). This program should be useful as a prelab exPartial scansofenunknowncantaining 12.8%Zr. 16.7%Cu,11.3%Na, 5.04% ercise before carrying out a real analysis. It could also K. and 10.9% Ba using atungslen tube and lithium fluoride (len)and ethylene he used as a laboratory substitute if no X-ray diamine btamate (right)analyzing crystals. equipment were available. Besides providing a fairly complete simulation of X-ray fluorescence analysis, this program can be used to demonstrate some of the oroblems in X-rav fluorescence work and how they . might . be solved. For example, i t is easy t o show how the spectrum ofihe exciting x-ray tube interferes with the analysis of some elements and how changing the tube can help. I t can be shown how two elements mieht interfere with each other and also how ehaneine the analvzine crvstal affects the soread
Eastern Washington University Cheney, Washington 49004
G. L. Breneman
Volume 56, Number 5, May 1979 1 303
