Accurate wave-number measurements of uranium spectral lines

Wave-number measurements were made on 10 uranium and 2 thorium transitions using the optogalvanic effect in a hollow-cathode discharge to position a single-frequency, cw dye laser to the peak of a transition. The wave number of the dye laser was measured by comparing it with the wave number of an iodine-stabilized He–Ne laser. The accuracy of the wave-number measurements was ±0.0006 cm−1. The data agree within ±0.002 cm−1 with previously reported uranium and thorium measurements whose estimated accuracy was ±0.003 cm−1.