A Compilation of Energy Levels and Wavelengths for the Spectrum of Neutral Beryllium (Be I)

In this compilation we have used data from some 20 references, only two of which were available to C. E. Moore for her 1949 Atomic Energy Levels tables. The new compilation thus includes significant revisions, extensions, and improvements of the earlier data for configurations of the types ${\text{1s}}^2\text{2snl}$ and ${\text{1s}}^2\text{2pnl}$ and also extends the energy range to higher configurations, including those involving 1$s$ electron excitation. The observed wavelengths for some 200 lines are given with their energy-level classifications. The wavelength measurements, which extend from 89 to 31 780 Å, were obtained from emission spectra of hollow-cathode and arc discharges, beam-foil spectra, and far-ultraviolet photoabsorption spectra. In addition to the energy levels derived from these spectra, we include levels obtained from multiphoton resonance-ionization mass spectrometry and projectile-Auger spectroscopy. We have evaluated a number of levels by using series formulas and/or theoretical results; these levels are more accurate than values derived from available wavelength measurements. Wavelengths calculated from energy-level differences are given for all lines; these “Ritz” wavelengths are more accurate than the observed values wherever the differences are significant.