Isospin-symmetry violating branch of 42Sc β+ decay

The branching fraction of the 42Sc 0+ ground state to the 0+ 1837-keV level of 42Ca was determined to be (1.03 +- 0.31) x 10-4 relative to the superallowed decay to the 0+42Ca ground state. The experiment was designed to eliminate possible spurious effects and systematic errors. Our result overlaps the larger of two recent measurements which were in rather poor agreement, and is half of that predicted by current microscopic calculations. The importance of this measurement in the extraction of the vector coupling constant G/sub V/ is discussed