Laser-Induced Fluorescence Studies Of U-Ii Produced By Photo-Ionization Of Uranium

Multiphoton ionization of uranium atoms followed by laser‐induced fluorescence detection of uranium ions is used to study the initial electronic state distribution of photon‐produced ions and the degree of ionization within the uranium vapor. Our experimental data clearly demonstrate that photoionization of uranium through the 50 701 cm−1 excited even levels using a broad band pulsed dye laser of 5915 A produces roughly 50% ground state ions and 50% metastably excited (289 cm−1) ions. The effective photoionization cross section is about 4.7×10−17 cm2. The subsequent dispersion of UII after photoionization appears to be caused by ambipolar expansion of ions and electrons in the plasma. The gA values for the 4050 and 3859 A transitions of UII are measured to be 0.86×108 and 2.8×108 s−1, respectively.