Structure of 10Be from the 12C 12C,14O 10Be reaction

The 12C 12C,14O two proton pick up reaction has been measured at 211.4 MeV incident energy to study the structure of states of 10Be up to excitation energies of 12 MeV. The measured partial angular distributions show pronounced oscillatory shapes, which were described by coupled reaction channels calculations. Spin parity assignments could be derived from these characteristic shapes and two definite assignments have been made. The state at 11.8 MeV has been identified as the 4 member of the ground state band, and the state at 10.55 MeV is assigned J pi 3 . At 5.96 MeV only the 1 1 member of the known 2 2 1 1 doublet is populated. The angular distribution of the peak at 9.50 MeV, which consists of several unresolved states, has been unfolded using contributions from known states at 9.56 MeV, 2 , and 9.27 MeV, 4 . The inclusion of a state at 9.4 MeV reported by Daito it et al. from the 10B t,3He 10Be reaction and tentatively assigned 3 improved the fit considerably. A K 2 band is formed with the 2 2 state as the band head and the 3 state as the second member. The structures of the K pi 0 1, 2 2, and 1 1 bands are discusse

Search for three alpha states around an 16^{16}O core in 28^{28}Si

We investigate the existence of weakly coupled gas-like states comprised of three $\alpha$ particles around an $^{16}$O core in $^{28}$Si. We calculate the excited states in $^{28}$Si using the multi-configuration mixing method based on the $^{16}$O + 3$\alpha$ cluster model. We also include the $^{16}$O + $^{12}$C and $^{24}$Mg + $\alpha$ basis wave functions prepared by the generator coordinate method. To identify the gas-like states, we calculate the isoscalar monopole transition strengths and the overlap of the obtained states with the geometrical cluster wave function and the Tohsaki-Horiuchi-Schuck-R\"{o}pke (THSR) wave function. The results show that the obtained fourth and twelfth states significantly overlap with the THSR wave function. These two states clearly coexist with the $^{16}$O + $^{12}$C cluster states, emerging at similar energies. The calculated isoscalar monopole strengths between those two states are significantly large, indicating that the states are members of the excitation mode. Furthermore, the calculated root-mean-squared (RMS) radii for these states also suggest that a layer of gas-like three $\alpha$ particles could exist around the surface of the $^{16}$O core, which can be described as a "two-dimensional gas" in the intermediate state before the Hoyle-like three $\alpha$ states emerge.Comment: 5 pages, 3 figure

New Measurement of the Direct 3α Decay from the 12C Hoyle State

Excited states in certain atomic nuclei possess an unusual structure, where the dominant degrees of freedom are those of α clusters rather than individual nucleons. It has been proposed that the diffuse 3α system of the 12C Hoyle state may behave like a Bose-Einstein condensate, where the α clusters maintain their bosonic identities. By measuring the decay of the Hoyle state into three α particles, we obtained an upper limit for the rare direct 3α decay branch of 0.047%. This value is now at a level comparable with theoretical predictions and could be a sensitive probe of the structure of this state

15O+α resonant elastic scattering to study cluster states in19Ne

Clustering phenomena are well known in nuclear physics for stable nuclei, both α-conjugate (N=Z, A=2N), like8Be,16O,20Ne, and non-α-conjugate, like6Li and7Li. In general, it is expected that light exotic nuclei may also exhibit cluster behavior. Moving out of the valley of stability configurations can be found where at least one of the clusters is unbound or weakly bound, thus not satisfying the strong internal correlation requirement of classical clusters. This is so-called exotic clustering. The study of such systems presents many difficulties, due, mainly, to the low intensities typical of radioactive ion beams. Therefore, few significant experimental studies have been performed so far. In this work we searched for α-cluster states in19Ne above its α-decay threshold measuring, for the first time, the15O(4He,4He) elastic scattering excitation function. Moreover, this study classified low-energy states in Ne in the astrophysically important region in this HCNO-break-out nucleus.European Unions Horizon 2020 65974

Oxygen-15+ resonant elastic scattering to study cluster states in 19Ne

The elastic scattering excitation function for 15O on 4He was measured - for the first time - by using the Inverse Kinematic Thick Target scattering method. The obtained spectrum was analysed in an R-matrix framework providing spectroscopic information for several states in the excitation energy of the nucleus 19Ne from 4.8 to 9 MeV. Eight of them are newly observed states. The set-up and the experimental technique will be described in detail and the results will be shown and discussed.European Unions Horizon 2020 65974

Particle-gamma coincidences and coplanarity in the 32S+24Mg^{32}S+^{24}Mg binary reaction

The reaction 32S (165.4 MeV) + 24Mg is studied using the binary reaction spec- trometer (BRS) coupled to the Euroball germanium array. Particle-particle-gamma and particle-gamma-gamma coincidences have been examined. The Z-identification, position and energy information for binary reaction products are shown together with the Doppler-shift corrected gamma-rays emitted from the fragments. Recent reports of evi- dence for hyper-deformation from angular correlations in similar data are also in- vestigated. Analogous out-of-plane angular correlations are observed but attributed to reactions with the target contaminants 16O and 12C

Evidence for triangular D3h symmetry in C 12

We report a measurement of a new high spin Jp = 5- state at 22.4(0.2) MeV in 12C which fits very well to the predicted (ground state) rotational band of an oblate equilateral triangular spinning top with a D_3h symmetry characterized by the sequence 0+, 2+, 3-, 4+/-, 5- with almost degenerate 4+ and 4- (parity doublet) states. Such a D_3h symmetry was observed in triatomic molecules and it is observed here for the first time in nuclear physics. We discuss a classification of other rotation-vibration bands in 12C such as the (0+) Hoyle band and the (1-) bending mode band and suggest measurements in search of the predicted ("missing") states that may shed new light on clustering in 12C and light nuclei. In particular the observation (or non-observation) of the predicted ("missing") states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha-particle composing the Hoyle state at 7.654 MeV in 12C.Comment: Accepted for Publication in the Physical Review Letter