6533b7cffe1ef96bd1258cd5

RESEARCH PRODUCT

Overlappingβdecay and resonance neutron spectroscopy of levels inKr87

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description

Energy levels in $^{87}\mathrm{Kr}$ have been studied, with special emphasis on the unbound region, using two different methods. The first method comprises neutron capture and transmission measurements on an enriched gas target of $^{86}\mathrm{Kr}$ using neutron time-of-flight techniques. In this way, neutron widths were determined for 39 resonances below 400 keV and capture areas for 14 resonances below 90 keV. The second method is a decay study of 56-s $^{87}\mathrm{Br}$ in which a level scheme for $^{87}\mathrm{Kr}$ has been established that shows 126 levels in the bound and 12 levels in the unbound region. A detailed comparison amongst the neutron resonance, the $\ensuremath{\gamma}$-ray decay, and available delayed neutron results has been made. Almost a one-to-one correspondence exists between the currently observed $p$-wave resonances below 250 keV and levels in $^{87}\mathrm{Kr}$ studied through delayed neutron emission. The overall $\ensuremath{\beta}$-strength distribution derived from the present data shows broad resonancelike structures. However, no marked selectivity is observed in the $\ensuremath{\beta}$ decay to individual levels in the unbound region of $^{87}\mathrm{Kr}$. The neutron capture cross section of $^{86}\mathrm{Kr}$ is found to be about 5 mb for 30-keV neutrons with a Maxwellian energy distribution. The future of delayed neutron spectroscopy as a new tool for obtaining level-density information is discussed.NUCLEAR REACTIONS $^{86}\mathrm{Kr}(n)$, ${E}_{n}=1\ensuremath{-}400$ keV, measured total $\ensuremath{\sigma}(E)$; $^{86}\mathrm{Kr}(n, \ensuremath{\gamma})$,, ${E}_{n}=1\ensuremath{-}90$ keV, measured ${\ensuremath{\sigma}}_{n\ensuremath{\gamma}}$; $^{87}\mathrm{Kr}$ deduced resonances, resonance parameters, neutron strength functions, Maxwellian average cross section; enriched target.RADIOACTIVITY $^{87}\mathrm{Br}$ [from $^{235}\mathrm{U}(n, f)$], measured ${E}_{\ensuremath{\gamma}}$, ${i}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}\ensuremath{\gamma}$-coinc; deduced $^{87}\mathrm{Kr}$ levels; deduced $^{87}\mathrm{Br}$ ground state $J$, $\ensuremath{\pi}$; Ge(Li) detector, mass separated source.