Diode laser-excited optogalvanic and absorption measurements of uranium in a hollow cathode discharge

Optogalvanic spectra for fifty two transition lines of uranium in the wavelength ranges of 662-683, 774-792, and 834-862 nm were measured by using external-cavity diode lasers. Among these transitions, 860.795 nm and 682.691 nm were chosen for a detailed investigation of the detection limit for uranium by wavelength modulation spectroscopy due to its stronger signal magnitudes. A detection limit of about 2 x 10(-5) absorbance achieved at 860.795 nm is more sensitive than that obtained at 682.691 nm, but the absorption spectrum at 682.691 nm is preferable to determine the isotope ratio due to the narrower hyperfine structure as well as the larger isotope shift. A preliminary result for an isotope ratio determination in a depleted sample is presented.