Ultraviolet transitions from the 2 /sup 3/P states of helium-like argon. [E2, 138 MeV, absolute wavelengths, beam--foil excitation, half-life

Abstract

This thesis describes the observation of two allowed electric dipole transitions in helium-like argon. The transitions are 2 /sup 3/P/sub 2/--2 /sup 3/S/sub 1/ and 2 /sup 3/P/sub 0/--2 /sup 3/S/sub 1/. These transitions were observed by using a vacuum ultraviolet monochromator to collect photons from decays-in-flight of a beam-foil excited argon ion beam. The ion beam was generated by the Lawrence Berkeley Laboratory heavy ion linear accelerator (SuperHILAC) and had a beam energy of 138 MeV with a charge current of roughly 500 nanoamperes. After initial observation, the lifetimes and absolute wavelengths of these transitions were measured. The results are tau(2 /sup 3/P/sub 2/) = 1.62 +- 0.08 X 10/sup -9/ sec, tau(2 /sup 3/P/sub 0/) = 4.87 +- 0.44 X 10/sup -9/ sec, lambda(2 /sup 3/P/sub 2/--2 /sup 3/S/sub 1/) = 560.2 +- 0.9A, and lambda(2 /sup 3/P/sub 0/--2 /sup 3/S/sub 1/) = 660.7 +- 1.1A. This work has demonstrated the observability of these transitions in high-Z ions using beam-foil excitation. Employing a new grazing-incidence spectrometer this work will be pursued in ions of higher Z. Accuracies of at least one part in a thousand should be attainable and will probe the radiative contributions to these transitions tomore » better than 10 percent in a previously unstudied region.« less