The usefulness of ion‐induced x‐ray yields to detect low‐Zimpurity atoms at low concentration in medium‐Ztargets and to locate their lattice sites in single crystals is established in this and the paper that follows. In paper I we describe the technique used with specific reference to phosphorus and sulfur implants in germanium crystals. Particular attention was given to the origin of the different components that constitute the backgrounds in the x‐ray energy spectrum. Peak‐to‐background ratios for these two impurity signals were then determined for H and He ions in the energy region from 0.5 to 2.0 MeV. Some results for N and Ar ions were also obtained. A beam of 0.5‐MeV H+gave optimum conditions for foreign atom location studies.