F. Hanappe

The 8He and 10He spectra studied in the (t, p) reaction

The low-lying spectra of 8He and 10He nuclei were studied in the 3H(6He, p)8He and 3H(8He, p)10He transfer reactions. The 0+ ground state (g.s.) of 8He and excited states, 2+ at 3.6–3.9 MeV and (1+) at 5.3–5.5 MeV, were populated with cross sections of 200, 100–250, and 90–125 μb/sr, respectively. Some evidence for a 8He state at about 7.5 MeV was obtained. We discuss a possible nature of the nearthreshold anomaly above 2.14 MeV in 8He and relate it to the population of a 1− continuum (soft dipole excitation) with a peak value at about 3 MeV. The lowest energy group of events in the 10He spectrum was observed at ∼ 3 MeV with a cross section of ∼ 140 μb/sr. We argue that this result is consistent with the previously reported observation of 10He providing the new 10He g.s. position at about 3 MeV

Evidences for resonance states in 5H

Resonance states of H-5 were investigated through the two-neutron transfer reaction t(t, P)(5) H. A triton beam at 57.5 MeV and a cryogenic liquid tritium target were used. The H-5 missing mass spectrum in triple coincidence, proton + triton + neutron, shows a resonance at 1.8 +/- 0.1 MeV above the t + 2n decay threshold. This energy is in good agreement with the result reported in Phys. Rev. Lett. 87 (2001) 092501. The resonance width, Gamma(intr) less than or equal to 0.5 MeV, is surprisingly small and difficult to reconcile with theory predictions

Soft dipole mode in 8He

The low-lying spectrum of 8He was studied in the 3H(6He, p)8He transfer reaction for small center of mass angles. The 0+ ground state (g.s.) of 8He and excited states, 2+ at 3.6–3.9 MeV and (1+) at 5.3–5.5 MeV, were populated with cross sections of 200, 100–250, and 90–125 μb/sr. Some evidence for the excited state at about 7.5 MeV can be found in the data. The possible nature of the near-threshold anomaly above 2.14 MeV in 8He is related to the population of a 1− continuum (soft dipole excitation) with a peak energy value at about 3 MeV. This assumption can probably resolve the problem of a large uncertainty existing in the experimental data on the 8He 2+ state energy.

Study of complete and incomplete fusion for loosely bound projectiles 6He and 6Li on 165Ho and 166Er targets

Complete fusion (CF) and incomplete fusion (ICF) reactions were studied for the cases of the loosely bound 6He and 6Li projectiles bombarding 166Er and 165Ho targets at energy of about 10 MeV/nucleon. Experiments were carried out to test an approach exploiting the measured intensities of γ rays emitted at the transitions between the yrast-band levels of reaction products formed after the termination of neutron evaporation. Partial waves feeding the CF reactions 165Ho (6Li, 5n) 166Yb and 166Er(6He, 6n) 166Yb as well as ICF 165Ho (6Li, α3n) 164Er and 166Er(6He, α4n) 164Er reaction channels were revealed from the obtained γ-ray data. The method of exit channel identification via the triple coincidence (γ1-γ2-light charged particle) was employed for these reactions study.

Complete and Incomplete Fusion of6He and6Li Projectiles with Medium Mass Targets at Energy ∼10 AMeV

Complete fusion (CF) and incomplete fusion (ICF) reactions were studied with the beams of loosely bound 6He and 6Li bombarding 166Er and 165Ho targets. Experiments were carried out to test an approach exploiting the measured intensities of y rays emitted at the transitions between the yrast-band levels of reaction products formed after the termination of neutron evaporation. Partial waves feeding the CF [ 165Ho(6Li,5n)166Yb, 166Er( 6He,6n)166Yb] and ICF [165Ho( 6Li,α3n)164Er, and 166Er( 6He,α4n)164Er] reaction channels were revealed from the obtained γ-ray data.

Resonance states of superheavy hydrogen nuclei obtained in transfer reactions with exotic beams

A resonance state situated at 1.8 +/- 0.1 and, most likely, another state positioned at 2.7 +/- 0.1 MeV above the t+n+n decay threshold were observed in the missing mass energy spectrum of the H-5 nucleus produced in the reaction H-3(t,p)H-5. The peak located close to E-5H = 1.8 MeV also was seen in the H-5 spectrum obtained from the energy distributions of 3H nuclei emitted in the reaction H-2(He-6,H-5)He-3. The width (Gamma(obs) less than or equal to 0.5 MeV) obtained for the two 5H resonance states is surprisingly small. A state of H-4 with E-res = 3.3 MeV and gamma(2) = 2.3 MeV was obtained in the reaction H-2(t,p)H-4 from the proton spectrum.