Updated System of S <sc>i</sc> Levels Using Fourier Transform Infrared Spectroscopy in the Range from 800 to 11,000 cm-1

In this study we report on high-precision laboratory measurements of transition wavenumbers for 172 atomic sulfur lines in the infrared region 800-11,000 cm(-1) using Fourier transform spectroscopy techniques. Our analysis includes 96 lines that have not been previously measured in the laboratory. We also correct several sulfur energy-level measurements reported in earlier studies. These refined measurements are important for a range of scientific disciplines, such as astrophysics, atmospheric chemistry, and combustion plasma physics. We have used the combined list of all observed lines to derive a refined set of sulfur energy levels. For about half of all nonautoionizing levels, the uncertainties have been reduced by a factor between 2 and 23. From the newly measured nonpenetrating (high-l) Rydberg levels we have also obtained the first ionization energy of the S atom, IE = 83,559.170(11) cm(-1), which is more accurate than the currently recommended value by 2 orders of magnitude. Our analysis has led to a significantly more accurate result than the earlier set of Ritz wavelengths with observed intensities reduced to a common uniform scale and an extended list of recommended transition probabilities.