High efficiency laser resonance ionization of plutonium
Three-step resonance photoionization spectra of plutonium have been studied with Ti:Sapphire lasers for the development of efficient laser ionization schemes for ultra-trace analysis of Pu isotopes by resonance ionization mass spectrometry. We observed eighteen intermediate excited states of even parity in the energy range 35568–36701 cm -1 , thirteen of them have not been previously documented, and a larger number of high-lying excited states and autoionizing states of odd-parity between 48238 and 49510 cm -1 . Three-color, three-photon ionization schemes via six intermediate states were evaluated under similar ion source operating conditions. This led to a highly efficient three-step scheme with an overall ionization efficiency of 51.1±1.3%, which is an order of magnitude improvement over the previously reported ionization efficiency for Pu.