high-voltage discharge of hydrogen with and without the presence of a source of potassium, potassium iodide, in the discharge was performed with a hollow cathode. It has been reported that intense extreme ultraviolet (EUV) emission was observed from atomic hydrogen and certain elements or certain ions which ionize at integer multiples of the potential energy of atomic hydrogen, 27.2 eV (Milis et al., 1999 Pacific Conference on Chemistry and Spectroscopy and the 35th ACS Western Regional Meeting, Ontario Convention Center, Ontario, CA, October 6-8, 1999; Mills et al., Int. J. Hydrogen Energy 2000;25:919; Mills, Int. J. Hydrogen Energy 2001;26:327; Mills, Lu and Onuma, Int. J. Hydrogen Energy 2001 in press; Mills et al., Int. J. Hydrogen Energy 2001;26:309; Mills et al,, June ACS Meeting, 29th Northeast Regional Meeting, University of Connecticut, Storrs, CT, June 18-21, 2000). Two potassium ions or a potassium atom may each provide an electron ionization or transfer reaction that has a net enthalpy equal to an integer multiple of 27.2 eV. The spectral lines of atomic hydrogen were intense enough to be recorded on photographic films only when KI was present. EUV lines not assignable to potassium, iodine. or hydrogen were observed at 73.0, 132.6, 513.6, 677.8, 885.9, and 1032.9 Angstrom. The lines could be assigned to transitions of atomic hydrogen to lower-energy levels corresponding to lower-energy hydrogen atoms called hydrino atoms acid the emission from the excitation of the corresponding hydride ions formed from the hydrino atoms.