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Register a new userObservation of the near-threshold intruder $0^-$ resonance in $^{12}$Be
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A resonant state at $3.21^{+0.12}_{-0.04}$,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and decay-width analysis. Gamow coupled-channel (GCC) and Gamow shell-model (GSM) calculations show the importance of the continuum-coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in $^{12}$Be and in its isotonic nucleus $^{11}$Li are comparably discussed.
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An experiment for $p(^{14}rm{C}$,$^{14}rm{C}^{*}rightarrow^{10}rm{Be}+alpha)mathit{p}$ inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 MeV/u. A series of $^{14}rm{C}$ excited states, including a new one at 18.3(1) MeV, were observed which decay to various states of the final nucleus of $^{10}rm{Be}$. A specially designed telescope-system, installed around the zero degree, played an essential role in detecting the resonant states near the $alpha$-separation threshold. A state at 14.1(1) MeV is clearly identified, being consistent with the predicted band-head of the molecular rotational band characterized by the $pi$-bond linear-chain-configuration. Further clarification of the properties of this exotic state is suggested by using appropriate reaction tools.
The production of $Sigma^{0}$ baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to $sqrt{s_{NN}}=3.18$ GeV) is studied with the detector set-up HADES at GSI, Darmstadt. $Sigma^{0}$s were identified via the decay $Sigma^{0} rightarrow Lambda gamma$ with subsequent decays $Lambda rightarrow p pi^{-}$ in coincidence with a $e^{+}e^{-}$ pair from either external ($gamma rightarrow e^{+} e^{-}$) or internal (Dalitz decay $gamma^{*}rightarrow e^{+} e^{-}$) gamma
The 0$^+_2$ state in $^{34}$Si has been populated at the {sc Ganil/Lise3} facility through the $beta$-decay of a newly discovered 1$^+$ isomer in $^{34}$Al of 26(1) ms half-life. The simultaneous detection of $e^+e^-$ pairs allowed the determination of the excitation energy E(0$^+_2$)=2719(3) keV and the half-life T$_{1/2}$=19.4(7) ns, from which an electric monopole strength of $rho^2$(E0)=13.0(0.9)$times10^{-3}$ was deduced. The 2$^+_1$ state is observed to decay both to the 0$^+_1$ ground state and to the newly observed 0$^+_2$ state (via a 607(2) keV transition) with a ratio R(2$^+_1$$rightarrow0^+_1/2^+_1$$rightarrow0^+_2$)=1380(717). Gathering all information, a weak mixing with the 0$^+_1$ and a large deformation parameter of $beta$=0.29(4) are found for the 0$^+_2$ state, in good agreement with shell model calculations using a new {sc sdpf-u-mix} interaction allowing textit{np-nh} excitations across the N=20 shell gap.
Excitation spectra of $^{11}$C were measured in the $^{12}$C$(p,d)$ reaction near the $eta$ emission threshold. A proton beam extracted from the synchrotron SIS-18 at GSI with an incident energy of 2.5 GeV impinged on a carbon target. The momenta of deuterons emitted at 0 degrees were precisely measured with the fragment separator FRS operated as a spectrometer. In contrast to theoretical predictions on the possible existence of deeply bound $eta$ mesic states in carbon nuclei, no distinct structures were observed associated with the formation of bound states. The spectra were analyzed to set stringent constraints on the formation cross section and on the hitherto barely-known $eta$-nucleus interaction.
A puzzle has long existed for the $alpha$-cluster content in the near-threshold 7.54 MeV state of $^{10}$Be. A new measurement was conducted to measure the cluster-decay partial width of this state, using the reaction $rm{^9Be}(rm{^9Be}, rm{^{10}Be}^{*} rightarrow alpha + rm{^6He})rm{^8Be}$ at 45 MeV beam energy. Special measures were taken to reduce the strong near-threshold background. The neutron-decay strength was also obtained based on the three-fold coincident measurement. A cluster-decay branching ratio of $(4.04 pm 1.26)times 10^{-4}$ is obtained, resulting in a reasonably large $alpha$-cluster spectroscopic factor. The present work confirms the formation of the $sigma$-bond molecular rotational band headed by the 6.18 MeV state in $^{10}$Be.
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