Nd III spectrum and energy levels

The classification of 432 transitions of Nd III from the Penning lamp spectra resulted in the determination of 144 energy levels of the 4f^4^, 4f^3^ 5d, 4f^3^ 6s, and 4f^3^ 6p configurations of Nd III, 105 of which were experimentally established for the first time. Of the 40 previously published Nd III levels, one was revised and 39 were confirmed. The results will not only benchmark and improve future semi-empirical atomic structure calculations of Nd III, but also enable more reliable astrophysical applications of Nd III, such as abundance analyses of kilonovae and chemically peculiar stars, and studies of pulsational wave propagation in these stars.