Abstract
Sprayed cathodes of calcium oxide on nickel alloy or platinum bases give a pale green luminescence when illuminated by light of wavelength less than 365 nm. The emission spectra show peaks at 340 nm and 540 nm; excitation spectra show peaks at 275 nm, 262 nm and 245 nm. The excitation peak at 275 nm is associated with the 340 nm luminescence and that at 262 nm with the 540 nm luminescence. On increasing the temperature of the cathode the 540 nm luminescence peak becomes relatively more prominent than the 340 nm peak. A tentative energy level diagram to account for these transitions is proposed.