GAMOW-TELLER STRENGTH TO K-38 FROM THE AR-38(P,N) REACTION AND CA-38(BETA(+)) DECAY

Gamow-Teller (1(+)) strength was studied in K-38 with the analog react ions Ar-38(p,n)K-38 and Ca-38(beta(+))K-38. The (p,n) reaction was per formed at 135 MeV using the beam swinger facility at the Indiana Unive rsity Cyclotron Facility. Excitation-energy spectra were measured at 1 5 angles between 0 degrees and 633. Neutron energies were measured by the time-of-flight method using a large-volume plastic scintillator ar ray at a flight path of 131.0 m. The overall energy resolution was 280 keV. Gamow-Teller (GT) strength was extracted from the measured angul ar distributions to discrete 1(+) final states. The beta-decay experim ent was performed with the ISOLDE on-line mass separator facility at C ERN. The beta-decay branching ratios were determined by observing the delayed gamma decays of K-38. These decay measurements provide an incr eased sensitivity over earlier measurements and are able to extract tr ansitions down to similar to 10(-4) of the strongest branches. The B(G T) values obtained from the two experiments are generally in good agre ement, except for the transition to the first 1(+) state at 0.46 MeV, which is observed to be much weaker in the (p,n) measurements. The bet a-decay measurements provide good resolution and high sensitivity whil e the (p,n) measurements extend the beta-decay measurements to higher excitation energies. The summed B(GT) strength is similar to 50% of th e simple Ikeda sum rule. The distribution bf GT strength is in reasona ble agreement with that predicted from a shell-model calculation using ''effective'' GT operators.