Gruen made contributions in a broad range of topics in the chemistry of materials : the definitive establishment of the 5f character of the actinides by the measurement and ligand field interpretation of magnetic moments at low temperatures; the creation of a solution chemistry in fused salts using spectroscopy to determine oxidation states, complex ions, and coordination equilibria of transition metal ions; the elucidation of the interactions of reactive molecular and atomic species with noble gas matrixes; the rational design of metal alloy hydrides for energy storage and heat pump applications; the determination of the energetics and depth of origin of sputtered species; ultrasensitive detection of atoms and molecules using laser Fluorescence and resonance ionization mass spectrometry; the discovery and development of a new chemical vapor deposition process for the synthesis of phase-pure nanocrystalline diamond films.
