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Proton–deuteron fusion reaction has been studied using a proton beam with an energy of 260 keV and a deuterium-implanted graphite target. The reaction product, 3He, usually de-excites by γ-ray emission. However, instead of a γ ray, 3He can emit an electron with a discrete energy of 5.6 MeV, due to electron screening in graphite. Such electrons were identified with the ΔE–E technique. The emission of fast electrons shows that electron screening causes the electrons to approach the nuclei during the reaction very closely. Different behavior of nuclear reactions at low and high energies was also demonstrated. Keywords: Nuclear astrophysics, Electron screening, Internal conversion, Fusion reactions, Radiative capture

The cross section for the 2H(p,$\gamma$)3He reaction was measured in the energy range E = 47–210 keV, relevant for primordial nucleosynthesis. A proton beam was incident on two deuterated titanium targets. The angular distribution of emitted $ \gamma$-rays was determined using two HPGe detectors, placed at $ 90^{\circ}$ and $ 135^{\circ}$ with respect to the incident beam direction. Results were compared with the latest ab initio theoretical calculation, including one- and many-body contributions. The predicted cross section and astrophysical S-factor are found to be in a very good agreement with measured values.

Excited states of nuclei near the doubly-magic nucleus Sn-100 were studied with the Ni-58+Cr-50 reaction. The experimental setup consisted of the GAMMASPHERE array augmented with light charged-particle and neutron detectors. Excited states were identified for the first time in the proton emitting nucleus Sb-105. Excitations across the N=Z=50 doubly closed shell were observed in Cd-99 and In-101. Some results of large-scale shell-model calculations are discussed.

High resolution spectra from fast proton radiative capture in {sup 208}Pb are presented for three energies of the incident protons: 14.8, 15.7, and 16.9 MeV. The collected spectra were analyzed with emphasis on the region of capture to unbound states in order to search for possible structure and to study the competition between two basically different phenomena: the statistical process versus the fluctuation effects in radiative capture to unbound final states. In the energy region of incoming protons considered in our experiment, the statistical processes modeled with a Hauser-Feshbach calculation dominate. The spectra of primary {gamma} rays, coincident with the low energy one from the decay of the f{sub 7/2} single-particle state, show a prominent structure which is predominantly of g{sub 9/2} character. The calculations of continuum spectra based on the extended direct-semidirect model and the Hauser-Feshbach statistical approach successfully reproduce the experimental data.

Gamma rays with energies up to 21 MeV were measured with Ge detectors. Such γ rays were produced in the 208Pb(p,γ)209Bi reaction. The position of the 2g9/2 single proton orbit in 209Bi has been determined indicating the size of the Z=126 shell gap.

Excited states in the proton emitter Sb-105 have been investigated for the first time. The nucleus was populated in the reaction Cr-50(Ni-58,1p2n). The GAMMASPHERE Ge-detector array was used together with Microball and the Neutron Shell for selection of the reaction channel. The experimental level scheme agrees well with results of a shell model calculation that uses realistic effective interactions derived from the CD-Bonn nucleon-nucleon interaction and Sn-100 as a closed-shell core.

High-energy γ rays produced by the 208 Pb ( p , γ) reaction were measured with the AFRODITE germanium detector array. The use of Ge instead of NaI detectors improved the energy resolution by more than a factor of 10 in the γ -ray energy range between 10 and 19 MeV. Proton captures into different single particles states in 209 Bi were thus clearly separated, most notably for the i 13/2 high-spin state. The measured excitation functions are in very good agreement with the predictions of the direct–semi-direct model, including captures to the i 13/2 state, for which the previous agreement had been poor.