Radiative Capture of Protons and Deuterons Into HELIUM-3

An investigation of the ('2)H(p,(gamma))('3)He(' )and ('1)H(d,(gamma))('3)He reactions has been made to provide precision measurements of angular distributions of both cross section and analyzing power in order to test current models of the three-body system. Angular distribution of cross section for the ('2)H(p,(gamma))('3)He reaction have been measured at proton beam energies of 6.5, 8.0, 11.0, 15.0, and 16.0 MeV at 13 to 17 angles. Angular distributions of analyzing power were also measured at both 8 and 16 MeV for 9 and 13 angles, respectively. The analyzing powers and cross sections were obtained for the(' (,1))H(d,(gamma))('3)He reaction at E(,p) = 1.62 MeV for 5 angles from 50(DEGREES) to 135(DEGREES). Finally, fore-aft asymmetries were measured in 1 meV steps between 6 and 16 MeV. We have used direct capture model calculations to compare with our experimental results. The ('3)He ground state wave functions were two-body (p+d) projections of three-body wave functions generated from Faddeev-type equations. Distorted waves were used in the continuum p+d channel. The direct radiative capture calculations assumed, E1, E2, and E3 multipole transitions. A comparison of the extracted a(,2) coefficients with the calculations indicates a sensitivity to the inclusion of D-state components in the ('3)He wave function. Theoretical three-body ('3)He ground state wave functions having D -state probabilities of 5-9% ((eta) = 0.050 to 0.038) are consistent with our data. The transition matrix analysis at 8 and 16 MeV including E1(s = 3/2) terms (transitions to the ('3)He D-state) result in (sigma)(E1; s = 3/2) of 1 to 6% and (sigma)(E2) of 1 to 3% in agreement with theoretical predictions. This is contrary to previous analyses which found a somewhat larger (sigma)(E2). The fore-aft asymmetry data is well accounted for by model calculations that consider only E1-E2 interference. Previous measurements of both (sigma)(,t) and (sigma)(90(DEGREES)) have varied widely. The present results confirm those measurements with large peak cross sections. The(' (,1))H(d,(gamma))('3)He reaction, when analyzed in conjunction with previous ('2)H(p,(gamma))('3)He(' )data at the same excitation energy, gives (sigma)(M1) of 1-8% with a good indication of M1(s = 3/2) transitions.