Energy dependence of the astrophysicalSfactor for theLi6(p,γ)Be7reaction

Polarized proton beams with energies from 80 to 130 keV have been used to determine the slope of the astrophysical S factor for the {sup 6}Li(p,{gamma}{sub 0}){sup 7}Be and {sup 6}Li(p,{gamma}{sub 1}){sup 7}Be reactions. The slope was determined from the relative yields at five incident proton energies. The slope of the S factor was found to be negative. The analyzing power measurements indicate that the reaction proceeds predominately by s-wave capture. The negative slope does not appear to be due to low-binding-energy effects, the effects of nearby resonances, or electron screening of the nuclei. A resonating group model calculation demonstrates a new mechanism for producing a negative slope at astrophysically relevant energies in radiative capture reactions.