New FTS measurements, optimized energy levels and refined VUV standards in the Ne III spectrum

All observed spectral lines of Ne III in the range 204 ? to 36 μm (277 cm^-1 to 490000 cm^-1) have been compiled and critically evaluated. 57 visible and ultraviolet lines of Ne III have been precisely measured using Fourier transform spectroscopy. An optimized level scheme has been derived from the total list of observed lines. Relative positions of about 180 out of a total of 226 previously known energy levels of Ne III have been determined with improved accuracy compared to previous studies. Excitation energies of almost all excited levels have been revised by (1.5–2.0) cm^-1. 127 precise wavelength standards in the region 210 ? to 2900 ? have been derived. Concepts of error current and covariance matrix have been implemented in a computational algorithm that permits one to derive the uncertainties of Ritz wavelength standards obtained from a set of least-squares-optimized energy levels. Nine new energy levels have been found, and 16 new transitions have been identified in the extreme ultraviolet region. The ionization potential has been increased by 4.5 cm^-1. The new value is ( ( ).