As typically embodied, the inventive method features bombardment of atomic nuclei with 3He ions in order to effect transmutation of atoms from a first atomic element to a second atomic element. Two notable inventive genres describe transmutation of: oxygen to nitrogen in an oxygen-containing target (e.g., including ZnO film); and, carbon to boron in a carbon-containing target (e.g., including SiC film). According to the former, transmutation of 16O to 15N occurs; more specifically, transmutation of 16O to 15O occurs via nuclear bombardment, and then transmutation of 15O to 15N occurs via decay by positron emission. According to the latter, transmutation of 12C to 11B occurs; more specifically, transmutation of 12C to 11C occurs via nuclear bombardment, and then transmutation of 11C to 11B occurs via decay by positron emission. Inventive practice frequently results in significant alteration of at least one physical property among: electronic carrier concentration; resistivity; photoconductivity; luminescence; morphology.