Qualitative X-ray fluorescence spectroscopy of metals - Moseley's law

Principle

Various metal samples are subjected to polychromatic X-rays. The energy of the resulting fluorescence radiation is analysed with the aid of a semiconductor detector and a multi channel analyser. The energy of the corresponding characteristic X-ray lines is determined and the resulting Moseley diagram is used to determine the Rydberg frequency and the screening constants.

Benefits

• Experience the essence of the Nobel Prize: Röntgen (1901)
• X-ray fluorescence analysis (XRF) of different alloys
• Other alloys are also possible
• X-ray energy detector (XRED) with multichannel analyzer (MCA) guarantess high counting rates without warm-up time

Tasks

1. Calibrate the semiconductor energy detector with the aid of the characteristic radiation of the  tungsten X-ray tube.
2. Record the spectra of the fluorescence radiation that are generated by the metal samples.
3. Determine the energy values of the corresponding characteristic K α- and K β-lines.
4. Determine the Rydberg frequency and screening constants with the aid of the resulting Moseley diagrams.

Learning objectives

• Bremsstrahlung
• characteristic X-radiation
• Absorption of X-rays
• Bohr's atom model
• Energy levels
• Moseley's law
• Rydberg frequency
• Screening constant
• Semiconductor energy detectors
• Multichannel analysers