Evidence for the First Excited State of

The ^{7}H system was populated in the ^{2}H(^{8}He,^{3}He)^{7}H reaction with a 26 AMeV ^{8}He beam. The ^{7}H missing mass energy spectrum, the ^{3}H energy and angular distributions in the ^{7}H decay frame were reconstructed. The ^{7}H missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2^{+} and 3/2^{+} doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2^{+} ground state of ^{7}H located at 1.8(5) MeV with quite a low population cross section of ∼25 µb/sr within angular range θ_{c.m.}≃(17°-27°).

Structure of 10He low-lying states uncovered by correlations.

The 0+ ground state of the 10He nucleus produced in the 3H(8He,p)10He reaction was found at about 2.1±0.2 MeV (Γ∼2 MeV) above the three-body ^{8}He+n+n breakup threshold. Angular correlations observed for ^{10}He decay products show prominent interference patterns allowing us to draw conclusions about the structure of low-energy excited states. We interpret the observed correlations as a coherent superposition of a broad 1- state having a maximum at energy 4-6 MeV and a 2+ state above 6 MeV, setting both on top of the 0+ state "tail." This anomalous level ordering indicates that the breakdown of the N=8 shell known in 12Be thus extends also to the ^{10}He system.

Observation of excited states in 5H.

The 5H system was produced in the 3H(t,p)5H reaction studied with a 58 MeV tritium beam at small c.m. angles. High statistics data were used to reconstruct the energy and angular correlations between the 5H decay fragments. A broad structure in the 5H missing mass spectrum showing up above 2.5 MeV was identified as a mixture of the 3/2+ and 5/2+ states. The data also present evidence that the 1/2+ ground state of 5H is located at about 2 MeV.

Superheavy hydrogen (5)H.

Experimental search for (5)H using a secondary beam of (6)He has been performed. The transfer reaction (1)H((6)He,(2)He)(5)H was studied by detecting two protons emitted from the decay of (2)He. A peak consistent with a (5)H resonance at 1.7+/-0.3 MeV above the n+n+t threshold was observed, with a width of 1.9+/-0.4 MeV. The angular distribution of the (1)H((6)He,(2)He)(5)H reaction was measured as well as the energy correlation of the two protons.