Measurements of ¹H(d(Combining right arrow above) ,γ)³He and ²H(p(Combining right arrow above),γ)³He at very low energies

L. Ma
H. J. Karwowski
C. R. Brune
Z. Ayer
T. C. Black
J. C. Blackmon
E. J. Ludwig
M. Viviani, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
A. Kievsky, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
R. Schiavilla, Thomas Jefferson National Accelerator Facility

Abstract

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.