Highly ionized uranium emission in the soft-x-ray region 50--100 A

Time-resolved uranium spectra emitted from a relatively low-density (n/sub e//similar to/10/sup 13/ cm/sup -3/), high-temperature (T/sub e//similar to/1 keV) plasma confined in the Texas experimental tokamak (TEXT) have been recorded in the 50--100 A range. It is found that narrow emission bands originating from transitions within charge states having 5p65d/sup k/ and 5s25p/sup k/ ground configurations, U XV to U XXXI, dominate these spectra. The identification of the transition arrays is based on the comparison with both ab initio intermediate-coupling relativistic level structure computations including configuration-interaction effects for the simple cases and, for complex charge states, with the predictions of the unresolved transition array model