First observation of excited states in [sup 199]At with the recoil filter detector

Prompt and delayed spectroscopy ofAt199

“…2(a). The gated spectrum confirms the doublet nature of the 600-keV peak, as reported by Styczeń et al [13]. In the present work the 600-keV transitions were placed lowest in a cascade on top of the ground state, according to the high intensity of the doublet peak, at variance with the previous work.…”

“…The 92-keV γ -ray transition reported in Ref. [13] was not observed. The intensity division between the transitions in the 600-keV doublet was made by comparing the intensity …”

“…It is evident that several γ -ray transitions (236, 373, 434, 609, and 670 keV) in the singles spectrum of Fig. 2(a) were also detected at the focal plane [13], placed to feed the expected 13/2 + isomer. This study focused on prompt γ -ray spectroscopy, and no high-lying isomer was reported.…”

“…At the same time, they noted that the level energies suggested by Styczeń et al [13] have to be revised. In the present work, the 573-keV γ ray is the most intense delayed transition assigned to 199 At [see Fig.…”

“…Męczyński et al [12] presented a strongly coupled rotational band on top of the 9/2 − ground state. Styczeń et al [13], however, placed it on top of the 13/2 + isomer, which was suggested to have an excitation energy of 466 keV and a half-life of the order of 1 µs. The isomeric decay itself was not detected.…”