Term analysis of the spectrum of neutral neptunium (Np I)

We have measured 6096 Np wavelengths with the 9 m Paschen-Runge spectrograph at Argonne and the Fourier transform facilities at Aime Cotton, of which 40% have been classified as transitions between 130 even levels and 329 odd levels. Most of the even levels and half of the odd levels have been identified by hyperfine structure and Zeeman data. The ground configuration is 5f46d7s2; the next configuration, 5f57s2, starts at 2831 cm−1. The low levels of 5f46d27s, 5f36d27s2, and 5f46d7s7p have been identified, and parameter fits made for 5f46d7s2 and 5f47s27p.