Deuterons

We discuss lattice simulations of light nuclei at leading order in chiral effective field theory. Using lattice pion fields and auxiliary fields, we include the physics of instantaneous one-pion exchange and the leading-order S-wave contact interactions. We also consider higher-derivative contact interactions which adjust the S-wave scattering amplitude at higher momenta. By construction our lattice path integral is positive definite in the limit of exact Wigner SU(4) symmetry for any even number of nucleons. This SU(4) positivity and the approximate SU(4) symmetry of the low-energy interactions play an important role in suppressing sign and phase oscillations in Monte Carlo simulations. We assess the computational scaling of the lattice algorithm for light nuclei with up to eight nucleons and analyze in detail calculations of the deuteron, triton, and helium-4.

Measurements of the electrical conductivity and deuteron NMR spin-lattice relaxation times (T,) in three different molecular weights of acid form NAFION conditioned at various levels of relative humidity have been carried out. Complex impedance studies were made along the plane of the film at frequencies from 10-10s Hz at room temperature and pressures up to 0.3 GPa. The high pressure electrical data were only obtained for water contents less than 8 wt%. The NMR measurements were also made at room temperature and pressures up to 0.25GPa. The NMR data are primarily for water contents greater than 6 wt%. The calculated activation volume exhibits a large decrease (from 16 to 3 cm3/mol) as the water content is increased from 2.4-8 wt%. In addition, the activation volumes are larger and the electrical conductivity is smaller for the higher molecular weight material. These results represent further evidence that the transport mechanism in low water content materials is dominated by segmental motions of the polymer chain and that proton transport and water molecular rotation are correlated. The activation volumes extracted from the NMR data show only a small further decrease as the water content is increased from 6-22wt%. Possible explanations for the high water content NMR pressure results are given.

A thin tritium target was bombarded by 14.1-MeV neutrons and the outgoing protons, deuterons and tritons were studied with a specially constructed proportional counter-scintillator telescope. The angular distribution for elastic scattering was obtained for neutron angles from 55° to 180° in the c.m. system. A previous calculation assuming a Serber interaction was shown to give a good fit to this angular distribution. Deuterons from the breakup reaction 3H(n, d)2n were detected at 8 lab = 0°, but no breakup protons were observed.

Measurements on the ratio between the contributions to the radiative neutron capture process by deuterons from states with total spin J = 1/2 and J = 3/2 are presented. It is shown that the outcome of these experiments can only be understood from the electromagnetic interactions with nucleons, mesons and nucleon resonances involving meson exchange. These mesons are the logical