A B S T R A C T T h e cross section and angular distribution o f gamma rays for t h c reactio~lD(pVr)He3 have been n~casured for proton energies from 275 Icev t o 1.75 hilev. For 275-lcev protons the total cross section is 0 . 9 7 f 0.11 ~uicrobarns and for 985-ltev protons i t is 3.5410.38 microbarns. 'The angular distribution has the form (sin2 B+b) where b is small. b is found t o increase w i t h decreasing proton energy, contrary t o some previous results fro111 this laboratory, and the energy dependence o f b and o f t h e cross section suggests that t h e sin" part o f the cross section is due t o t h e capture o f p-wave protons and the 2, part is clue t o s-wave proton capturc.

The yield and angular distribution of the γ rays from the reaction D(p, γ) He3 have been measured with thick heavy-ice targets in the energy range from 24 kev to 48 kev. Assuming a simplified energy dependence the results have been analyzed to give cross sections for p-wave and s-wave capture. At 25 kev in the laboratory system, the cross sections are[Formula: see text]The astrophysical S-factors in the center-of-mass system below 40 kev have been found to be[Formula: see text]for E in center-of-mass kilovolts and[Formula: see text]independent of energy giving a total S-factor for low energies[Formula: see text]with E in center-of-mass kilovolts.

The T(α,γ)Li7 reaction has been observed using thin targets of tritium absorbed in zirconium bombarded by singly charged helium ions of energy from 0.5 Mev to 1.9 Mev. The cross section rises smoothly with energy in a fashion characteristic of a direct radiative capture process. The ratio of the intensities of transitions to the first excited state at 478 kev and to the ground state is 0.40 ± 0.05. The angular distribution is, to within errors, isotropic at Eα = 0.8 Mev but is significantly higher at 0° than at 90° for Eα = 1.6 Mev. The total capture cross section at a mean alpha-particle energy in the target of 1.32 Mev is 3.58 ± 0.60 microbarns and the corresponding astrophysical S factor is 0.064 ± 0.016 kev barn in the center of mass system. The results are compared with recent theoretical results on the direct radiative capture process.

The cross section for the direct radiative capture of protons by 16O has been measured relative to the proton elastic scattering cross section for energies from 800 to 2400 keV (CM). The elastic scattering cross section was normalized to the Rutherford scattering cross section at 385.5 keV. The capture cross section for the reaction 16O(p,γ)17F, which plays a role in hydrogen burning stars, has been extrapolated to stellar energies using a theoretical model which gives a good fit to the measured cross sections. The model involves calculation of electromagnetic matrix elements between initial and final state wave functions evaluated for Saxon–Woods potentials with parameters adjusted to fit both elastic scattering data and binding energies for the ground and first excited states of 17F. Cross sections for capture to the 5/2+ ground and 1/2+ first excited states of 17F in terms of astrophysical S factors valid for energies ≤ 100 keV have been found to be: S5/2+ = (0.317 + 0.0002E) keV b (± 8%); S1/2+ = (8.552 − 0.353E + 0.00013E2) keV b (± 5%).

Total cross sections and measurements of the small isotropic component of the γ-ray yield from the reaction D(p, γ)3He have been determined in the energy range from 57 to 1100 KeV using gas and deuterated polyethylene targets. The results are compared with some theoretical predictions.