Abstract
We have performed the first direct measurement of the 38Kðp; γÞ39Ca reaction using a beam of radioactive 38K. A proposed l ¼ 0 resonance in the 38K þ p system has been identified at 679(2) keV with an associated strength of 120 þ50 −30 meV. Upper limits of 1.16 (3.5) and 8.6 (26) meV at the 68% (95%) confidence level were also established for two further expected l ¼ 0 resonances at 386 and 515 keV, respectively. The present results have reduced uncertainties in the 38Kðp; γÞ39Ca reaction rate at temperatures of 0.4 GK by more than 2 orders of magnitude and indicate that Ar and Ca may be ejected in observable quantities by oxygen-neon novae. However, based on the newly evaluated rate, the 38Kðp; γÞ39Ca path is unlikely to be responsible for the production of Ar and Ca in significantly enhanced quantities relative to solar abundances.