A nondestructive physical method used for chemical elemental analysis of materials in the solid or liquid state. The specimen is irradiated by photons or charged particles of sufficient energy to cause its elements to emit (fluoresce) their characteristic x-ray line spectra. The detection system allows the determination of the energies of the emitted lines and their intensities. Elements in the specimen are identified by their spectral line energies or wavelengths for qualitative analysis, and the intensities are related to their concentrations for quantitative analysis. Computers are widely used in this field, both for automated data collection and for reducing the x-ray data to weight-percent and atomic-percent chemical composition or area-related mass (of films).