Peter Schury edited untitled.tex  over 8 years ago

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In preliminary work towards No and Lr mass measurements (NP1306-LINAC07) we made precision mass measurements of $^{205,206}$Fr and $^{201}$At and rough mass measurements of $^{201}$Bi, $^{201, 205}$Po, $^{205, 206}$At and $^{205, 206}$Rn \cite{Schury_2015}. These measurements were achieved with only 6 hours of machine time, during which the system efficiency was $\approx$0.05\%. We found deviations from literature values in this data set. As shown in Fig.~\ref{figA=205_206}, we have demonstrated an ability to measure multiple isobaric chains simultaneously. This will enable a very efficient survey of the general mass landscape in this region.  \subsection{Survey of mass landscape}  Particularly for Ac, Th, and Pa isotopes in this region the mass landscape is not well-studied.  The region has very few directly measured mass values, and where masses are directly measured they tend to have been done at ESR \cite{Litvinov_2008} and could benefit from a cross-check by an alternate method. \subsection{Determination of isomeric production ratios}  The large number isomeric states known to exist in this region provide us with a special means to investigate the nuclear structure in this region. It is generally understood that direct production (e.g. by fragmentation or complete fusion) of nuclei can be na\;{i}vely understood, to zeroth-order, to populate spin states with a probability proportional to $I(I+1)$. Historically, studies of isomeric ratios \cite{Bowry_2013}\cite{de_Jong_1997} have measured the decay of isomeric and ground states to infer the relative populations. While such studies are the only means to address short-lived ($T_{1/2}\ll$1~ms) isomeric states, they require corrections for detector efficiencies, et cetera. By direct mass measurements, we will determine the production ratios without need for such corrections.