As the centenary of H. G. H. Moseley's untimely passing approached, the authors undertook an evaluation of Moseley's work as the basis for an undergraduate laboratory experiment. Using a modern solid-state detector and low activity sources, characteristic K X-rays were excited and detected without the use of a vacuum chamber, from a selection of elemental metal foil samples from Ti to Er. The authors introduce first order relativistic corrections into the experimental analysis to obtain better fits for K X-ray energies that deviate substantially from Moseley's original law for elements beyond the first row transition metals. The experimental set up is described in detail, and the data and conclusions are readily reproducible by undergraduate students in the span of a couple of typical lab sessions.
The CZT detector used became available as the result of a research equipment upgrade. A 3 mm × 3 mm CdTe detector, with integrated power supplies and digital pulse processor, with characteristics comparable to the CZT detector and analog MCA used in these experiments, is commercially available from Amptek for $7,900.
We made use of 241Am sources recycled from discarded smoke detectors. Cobalt-57 sources could be used instead to increase the range of measurable elements. The incremental cost would vary with the source configuration selected but individual unmounted 57Co sources are available commercially from suppliers such as Spectrum Techniques for about $100 each.
A basic selection of six first-row transition metal foils (>99.9% pure) can be obtained from suppliers such as Alfa Aesar for about $150. The more extensive selection of 17 foils needed to fully reproduce our results would cost about $650. A plastic sample stand similar to the one used here is available from suppliers such as Spectrum Techniques for about $100.