A COMPILATION OF ENERGY-LEVELS AND WAVELENGTHS FOR THE SPECTRUM OF SINGLY-IONIZED OXYGEN (O-II)

We have assembled a complete list of the most accurately measured wave lengths for all classified lines of O II. The data are based mainly on recent extensions of the observations and analysis of this spectrum c arried out at the University of Lund, Sweden. We derived new optimal v alues for the energy levels using a computer code and the observed wav elengths for all classified lines. Relevant astrophysical wavelength m easurements, appropriately weighted, were included in the level-optimi zation calculation. The tabulated data include about 1000 observed lin es (376-11 663 angstrom) classified as transitions between 125 odd-par ity and 133 even-parity levels. In addition to the observed wavelength values, wavelengths calculated from wavenumber differences of the lev els are given for all observed lines and for more than 200 predicted l ines that have not yet been observed. The calculated wavelengths are g enerally more accurate than the observed values, the most accurate cal culated values (uncertainties 0.0005 to 0.0020 angstrom) being in some cases more accurate than the observed wavelengths by up to an order o f magnitude. Vacuum wavelengths are given for all lines, and wavelengt hs in air are also included for the region above 2000 angstrom.