Joe has done research on the spectra of rare earth atoms, spectra of highly ionized atoms, hyperfine structure, and design of optical spectrometers. Current interests include spectra of ionized atoms of importance for diagnostics of controlled fusion plasmas (Zr VI, Nb IV, Mo VI), radiometry of fluorescent-lamp-type discharges in the ultraviolet, and critical compilations of atomic spectra (Ga, W, Ni-like ions).