Journal or Book Title
Physical Review Letters
We present the N4,5 appearance-potential spectrum of La. Structure exists at energies lower than the threshold energy for transitions terminating at the Fermi level. Several similarities between optical absorption spectra and our results are discussed. These results contradict the simple model usually used to interpret appearance-potential spectra and emphasize the need for a new theory.
The American Physical Society
Smith, R. J.; Piacentini, M.; and Lynch, David W., "Multiplet Structure below "Threshold" in Appearance-Potential Spectra—Lanthanum N4,5" (1975). Physics and Astronomy Publications. 44.