Measurements of 1H(d(Combining right arrow above) ,γ)3He and 2H(p(Combining right arrow above),γ)3He at very low energies
Angular distributions of the analyzing powers iT11 , T20, and T22 for 1H(d(Combining right arrrow above),γ)3He at 40≤Ec.m.≤110 keV and the angular distribution of the analyzing power Ay for 2H(p(Combining right arrow above),γ)3He at 70≤Ec.m.≤210 keV have been measured for the first time. In addition, absolute differential cross sections for proton-deuteron capture have been determined for Ec.m. = 15, 108, 133, and 173 keV. Thick ice or heavy ice targets and two large-volume, high-purity Ge γ-ray detectors were used. Results are in general agreement with an exact three-body calculation utilizing a realistic nucleon-nucleon potential. The vector-polarization observables are found to be especially sensitive to meson-exchange-current effects. The extracted S(0) value for proton-deuteron capture is ∼25% lower than that presently used in astrophysical calculations. An expression for the thermonuclear reaction rate below 10 GK is given.