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 reactions Ar-38(p,n)K-38 and Ca-38(beta(+))K-38. The (p,n) reaction was performed at 135 MeV using the beam swinger facility at the Indiana University Cyclotron Facility. Excitation-energy spectra were measured at 15 angles between 0 degrees and 633. Neutron energies were measured by the time-of-flight method using a large-volume plastic scintillator array at a flight path of 131.0 m. The overall energy resolution was 280 keV. Gamow-Teller (GT) strength was extracted from the measured angular distributions to discrete 1(+) final states. The beta-decay experiment was performed with the ISOLDE on-line mass separator facility at CERN. The beta-decay branching ratios were determined by observing the delayed gamma decays of K-38. These decay measurements provide an increased sensitivity over earlier measurements and are able to extract transitions down to similar to 10(-4) of the strongest branches. The B(GT) values obtained from the two experiments are generally in good agreement, 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 beta-decay measurements provide good resolution and high sensitivity while the (p,n) measurements extend the beta-decay measurements to higher excitation energies. The summed B(GT) strength is similar to 50% of the simple Ikeda sum rule. The distribution bf GT strength is in reasonable agreement with that predicted from a shell-model calculation using ''effective'' GT operators.