MEASUREMENTS OF H-1((D)OVER-RIGHT-ARROW,GAMMA)(3)HE AND H-2((P)OVER-RIGHT-ARROW,GAMMA)HE-3 AT VERY-LOW ENERGIES

Angular distributions of the analyzing powers iT(11), T-20, and T-22 f or H-1((d) over right arrow,gamma)He-3 at 40 less than or equal to E(c .m.)less than or equal to 110 keV and the angular distribution of the analyzing power A(y) for H-2((p) over right arrow,gamma)He-3 at 70 les s than or equal to E(c.m.)less than or equal to 210 keV have been meas ured for the first time. In addition, absolute differential cross sect ions for proton-deuteron capture have been determined for E(c.m.) = 75 , 108, 133, and 173 keV. Thick ice or heavy ice targets and two large- volume, high-purity Ge gamma-ray detectors were used. Results are in g eneral agreement with an exact three-body calculation utilizing a real istic nucleon-nucleon potential. The vector-polarization observables a re found to be especially sensitive to meson-exchange-current effects. The extracted S(0) value for proton-deuteron capture is similar to 25 % lower than that presently used in astrophysical calculations. An exp ression for the thermonuclear reaction rate below 10 GK is given.