A. A. Korsheninnikov

Measurements of interaction cross sections for light neutron-rich nuclei at relativistic energies and determination of effective matter radii

Abstract We measured the interaction cross sections ( σ I ) of 10,11B, 12–20C, 14–23N, 16–24O and 18–26F on carbon targets at energies of around 950 A MeV. We then deduced the effective matter radii of the nuclei by a Glauber-model analysis. Based on the assumption of a core plus a valence neutron structure, we applied a Glauber-model analysis for a few-body system adapted for nuclei with an odd neutron number. We also deduced the effective nucleus-matter densities as well as some spectroscopic information for selected nuclei. Evidence for a one-neutron halo structure was found for 22N, 23O and 24F, as well as 19C.

Observation of 10He

Abstract The reactions 11 Li + CD 2 → 10 He + X and 11 Li + C → 10 He + X at a beam energy of 61A MeV have been studied by measuring the triple coincidence of 8He and two neutrons. Experimental data show a peak that can be explained as a resonance 10He, which is unbound by 1.2±0.3 MeV and its width is less than 1.2 MeV. Theinvariant mass spectra of 8He+n show a peak that is consistent with the decay 10 He → 8 He + n + n .

Scattering of radioactive nuclei 6He and 3H by protons: Effects of neutron skin and halo in 6He, 8He, and 11Li

In an experimental study of 6He+p and 3H+p collisions at ∼70 A MeV, the elastic scattering angular distributions were measured and the known excited state 6He1.8∗ was observed. Comparative analysis of existing experimental data on proton elastic scattering by 4He, 6He, 6Li, 8He, 9Li, and 11Li was performed. Effects of valence neutrons were investigated using the eikonal approach. A difference between 11Li and 6,8He was found.

Spectroscopy of 12Be and 13Be using a 12Be radioactive beam

Abstract We have studied 12 Be + p elastic and inelastic scattering and observed new levels of 12 Be at E 12 Be ∗ = 8.6, 10 and ∼ 14 MeV in the vicinity of He-emission thresholds, which can be candidates for states having an exotic cluster structure with He-like subsystems. Some new states were tentatively assigned to 13 Be in studies of the d( 12 Be, p) reaction.

Experimental study of 8He + p elastic and inelastic scattering

Abstract An experimental study of 8He + p elastic scattering and a search for 8He∗ as observed in two independent experimental methods. The obtained parameters of the excited state are E 8 He ∗ = 3.57±0.12 MeV , Γ =0.5±0.35 MeV, Γ 4 He+4n /Γ 6 He+n+n ⩽ 5% . Angular distributions for elastic and inelastic scattering are measured. The inelastic angular distribution is consistent with Jπ = 2+ for 8He3.55∗.

Nuclear radii of 17,19B and 14Be

Abstract The interaction cross sections ( σ I ) of light radioactive nuclei close to the neutron drip line ( 17,19 B, 14 Be) have been measured at around 800 A MeV. The effective root-mean-square (r.m.s.) matter radii of these nuclei have been deduced from σ I by two different methods, a Glauber-type calculation based on the optical limit approximation and a few-body reaction model. The deduced radii from both approaches agree with each other within experimental uncertainty. The r.m.s. radii of 17 B (2.99±0.09 fm) and of 14 Be (3.10±0.15 fm) in this work are consistent with the previously determined values, and have a higher accuracy. The r.m.s. radius of 19 B (3.11±0.13 fm) was newly determined. Assuming a “core plus 2n” structure in 17 B and 14 Be, the mixing of ν (2 s 1/2 ) and ν (1 d 5/2 ) was studied and the s -wave spectroscopic factor is found to be 36±19% and 47±25%, respectively. A valence radius analysis suggests a “core plus 4n” structure in 19 B.

Quasifree nucleon-knockout reactions from neutron-rich nuclei by a proton target: p(6He,pn)5He, p(11Li,pn)10Li, p(6He,2p)5H, and p(11Li,2p)10He

Abstract Quasifree neutron-knockout (p,pn) reactions by a proton target from neutron-rich nuclei, 11 Li ( 6 He), were used to study the structure of 10 Li ( 5 He) and the momentum distribution of halo neutrons. Quasifree proton-knockout (p,2p) reactions from 11 Li ( 6 He) projectiles to 10 He( 5 H) resonances were also observed.

Nuclear-Reaction Cross-Sections at High Energies and Radii of Radioactive Nuclei. Radius of the 6He Nucleus

The cross-section of the radioactive 6He nucleus interaction with 9Be, 12C and 27Al nuclei is calculated at the 6He energies of 790 MeV/nucleon with the 6He density parametrization from the microscopic α + 2 model. It has turned out that the results are not sensitive to the parametrization form. Reliability of the simple quasi-Glauber-type calculation of interaction cross-sections of nuclei is studied with the aim of determining their matter radii, and the radius value for the 6He nucleus is estimated.

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