Following the successes with noble gas pumping, various laboratories undertook new NPL studies with three main goals: development of shorter wavelength lasers, lower neutron thresholds, and improved efficiencies. A NPL with visible output was developed in 1977 by a University of Illinois/Sandia team using an He-Hg charge exchange scheme [20]. Even shorter wavelengths were predicted when Miley’s team reported in 1978, for the first time, that gain had been measured with nuclear pumping of excimers [55]. Then, in the search for lower thresholds the University of Illinois group discovered a new class of NPLs where lasing occurs in a minority species (i. e., “impurity” lasers). The first such laser used small concentrations of N2 in neon [56]. Subsequently, a low-threshold (0.04 W/cm3 pump power) laser was developed using carbon from the dissociation of CO and CO2 during irradiation [57]. Later, an 3He-Ne laser with an even lower threshold was reported at the University of Florida, but the results are disputed [58, 59]. Later, gain measure­ments were reported on 3He-Ne at low fluxes or order 108 n/cm2 s [60].