Assignment of unclassified lines in Tb I through high-resolution laser-fluorescence measurements of hyperfine structure

It is demonstrated that high-resolution measurements of the hyperfine structure of unclassified spectral lines can be used in many cases to establish uniquely the classification of the lines if the structure of the low levels of the atom is already well understood. Examination of nine lines in Tb I confirms the previous classification in six cases, requires some modification of the previous assignment in one case, and gives the classification for two previously unassigned lines. One of the newly classified lines (lambda5795.64) is the first line found between 4338 and 10 239 A to connect with the Tb I atomic ground state. The Doppler-free laser-atomic-beam technique was used for the study. New hfs results are given for two even levels and eight odd levels of Tb I