title: High precision measurement of the superallowed 0+ --> 0+ beta decay of 22Mg.
abstract: The half-life, 3.8755(12) s, and superallowed branching ratio, 0.5315(12), for 22Mg beta decay have been measured with high precision. The latter depended on gamma-ray intensities being measured with an HPGe detector calibrated for relative efficiencies to an unprecedented 0.15%. Previous precise measurements of 0+ --> 0+ transitions have been restricted to the nine that populate stable daughter nuclei. No more such cases exist, and any improvement in a critical Cabibbo-Kobayashi-Maskawa unitarity test must depend on precise measurements of more exotic nuclei. With this branching-ratio measurement, we show those to be possible for T(z)=-1 parents. We obtain a corrected Ft value of 3071(9) s, in good agreement with expectations.
authors.affiliation: Cyclotron Institute, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Hardy
authors.forename: V E
authors.initials: VE
authors.lastname: Iacob
authors.forename: M
authors.initials: M
authors.lastname: Sanchez-Vega
authors.forename: R G
authors.initials: RG
authors.lastname: Neilson
authors.forename: A
authors.initials: A
authors.lastname: Azhari
authors.forename: C A
authors.initials: CA
authors.lastname: Gagliardi
authors.forename: V E
authors.initials: VE
authors.lastname: Mayes
authors.forename: X
authors.initials: X
authors.lastname: Tang
authors.forename: L
authors.initials: L
authors.lastname: Trache
authors.forename: R E
authors.initials: RE
authors.lastname: Tribble