Abstract
The first results of a continuing analysis indicate that the ground configuration of the first ion of protactinium is 5ƒ27s2, the ground level being 3H4. 656 lines have been classified as combinations between 25 low-even and 164 high-odd energy levels; these represent approximately 35% of the lines that have been assigned to the second spectrum of protactinium. Four other low-lying levels have been assigned to the 5ƒ26d7s configuration. The importance of the use of hfs measurements in the level-searching program is stressed.

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