Magneto-optic Trapping ofβ-Decaying38Km,37Kfrom an on-line Isotope Separator

Abstract

A magneto-optic trap (MOT) can provide a well-polarized, backing-free, localized source of radioactive atoms for $\ensuremath{\beta}$-decay experiments. We have trapped approximately 6000 atoms of ${}^{38}{\mathrm{K}}^{m}$ ( ${t}_{1/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.925\mathrm{s}$) and 2000 atoms of ${}^{37}\mathrm{K}$ (1.226 s) produced at the TRIUMF on-line separator TISOL in a vapor-cell MOT. We have measured optical isotope shifts and deduced the nuclear charge radii, which show an unusual lack of change at the neutron number $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}20$ shell closure. Plans include a search for scalar contributions to the ${\ensuremath{\beta}}^{+}$- $\ensuremath{\nu}$ correlation in the ${0}^{+}\ensuremath{\rightarrow}{0}^{+}$ decay of ${}^{38}{\mathrm{K}}^{m}$.