Narrow Results

The Coulomb dissociation of the proton-rich nuclei ³¹Cl was studied experimentally using ³¹Cl beams at 58 MeV/nucleon with a lead target. The relative energy between the reaction products, ³⁰S and proton, was obtained. The first excited state in ³¹Cl was observed which is relevant to the resonant capture of stellar ³⁰S(p,γ)³¹Cl reaction.

The parametrization schemes based on interaction radius and touching spheres (ts) commonly used for the determination of minimum value of impact parameter $(b_{\mathrm{\text{min}}})$ in the above barrier Coulomb excitation experiments are modified by incorporating an energy-dependent term. The modification leads to about 13% improvement in the value of $b_{\mathrm{\text{min}}}$ for a variety of projectile target combinations at above Coulomb barrier incident energies.

We have investigated the role of central depression parameter on the estimation of survival probability, the Coulomb excitation cross-sections and absorption effects of ${}^{80}\mathrm{\text{Kr}}+{}^{197}\mathrm{\text{Au}}$ system. The variation in central depression is found to be affecting all the above-mentioned quantities significantly. The survival probability and the Coulomb excitation cross-section are found to be decreasing with increase in $w$ while the absorption effects are found to be increasing.

We have investigated the absorption effects in the Coulomb excitation of neutron-rich ^38,40,42S-isotopes on Au target at energies around 40 MeV/A within the framework of the relativistic Coulomb excitation (RCE) theory. It has been found that when the minimum impact parameter is taken as sum of the radii of the interacting nuclei the Coulomb excitation cross section reduces by 19–23% due to absorption effects. In addition, the absorption effects have been found to be marginal at beam energies more than 200 MeV/A.

In this paper, we investigate the effect of simultaneous variation of surface diffuseness and central depression, in case of model-dependent Fermi matter density distributions, on the estimation of survival probability, Coulomb excitation cross-section and absorption effects for ${}^{80}\text{Kr}{+}^{197}$ Au system. Further, the role of model-dependent Fermi matter density distribution and model independent $\text{D}1\text{S}$ matter density distribution has also been investigated in the estimation of the above-mentioned quantities. The simultaneous variation of the parameters of the model-dependent density distribution and choice of the density distribution are found to be affecting all the above-mentioned quantities significantly and hence plays a crucial role in the analysis of the Coulomb excitation experiments also.

Two-proton radioactivity studies have been performed on excited states of ¹⁸Ne produced by ²⁰Ne fragmentation at the FRS of the Laboratori Nazionali del Sud and excited via Coulomb excitation on a ²⁰⁹Pb target. The ¹⁸Ne levels decay has been studied by complete kinematical reconstruction. In spite of the low statistic, the energy and angular correlations of the emitted proton pairs indicate the presence of ²He emission toghether with the democratic decay.

Mixed-symmetry states have been studied in various vibrational nuclei by electromagnetic probes using the techniques of electron scattering and Coulomb excitation. An inelastic electron scattering experiment on ⁹⁴Mo has been performed at the Darmstadt S-DALINAC. The technique is particularly sensitive to nuclear one-phonon excitations and shown to be a valuable tool for investigating one- and two-phonon states with mixed proton-neutron symmetry. A series of Coulomb excitation experiments has been performed at Argonne National Laboratory. Absolute transition strengths in ¹³⁴Xe are derived. The main fragment of the one-phonon mixed symmetry state has been identified from the strength distribution.

Results of two experimental campaigns are presented investigating shell structure in neutron-rich nuclei near ⁵⁴Ca and ¹³²Sn, respectively. In the first experiment excited states in ⁵⁵Ti were investigated at the middle focus of the GSI FRS via one-neutron knock-out from ⁵⁶Ti. Longitudinal momentum distributions were measured inclusively and in coincidence with a newly discovered gamma-ray at 955 keV detected by the MINIBALL gamma-ray detector array. From the momentum distributions the νp_1/2 single-particle structure of the ground state was determined for the first time while the excited state at 955 keV is identified as the νp_3/2 single-particle state. Secondly, results from the Coulomb excitation of neutron-rich nuclei ^122,124,126Cd, ^{138,140,142,144}Xe are presented. These experiments were performed at the REX-ISOLDE accelerator at CERN also using the MINIBALL array. The obtained B(E2)-values follow the expected systematic behavior that correlates the energy of the first excited 2⁺ state with the B(E2)-values and also agree well with the results of theoretical predictions.

The octupole strength present in the neutron-rich, radiocative nucleus ¹⁴⁶Ba has been experimentally determined for the first time using Coulomb excitation. To achieve this, A=146 fission fragments from CARIBU were post-accelerated by the Argonne Tandem Linac Accelerator System (ATLAS) and impinged on a thin ²⁰⁸Pb target. Using the GRETINA γ-ray spectrometer and the CHICO2 heavy-ion counter, the reduced transition probability B(E3; 3⁻→0⁺) was determined as $48\left(\begin{array}{l}+21\\ -29\end{array}\right)$ W.u. The new result provides further experimental evidence for the presence of a region of octupole deformation surrounding the neutron-rich barium isotopes.

The use of α-transfer reactions to populate states in nuclear species that cannot be produced in the present radioactive beam facilities is presented. Some examples of the use of these type of reactions to measure nuclear g factors and lifetimes will be discussed. The advantages and challenges for the use of α-transfer reactions with stable and radioactive beams will be discussed.

The lifetimes and the relative g factors of the first excited states in ^104,106,108Pd are reported here. The first state in these Pd isotopes were excited by inverse kinematics Coulomb excitation on a ²⁴Mg target and the lifetime was measured by the Recoil Distance Doppler Shift with the New Yale Plunger Device combined with the SPEEDY array of Clover detectors. The results show the feasibility of the new method, which should be applicable to experiments with radioactive ion beams.

New g-factor measurements by the recoil in vacuum method are discussed. The stable even tin isotopes, neutron-rich ^126,128Sn, and tellurium isotopes including neutron-rich semimagic ¹³⁴Te, have been studied. The experiments were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) by Coulomb exciting ~ 3 MeV/u beams in inverse kinematics on C and Ti targets, and using the CLARION+HyBall arrays to observe the perturbed particleangular correlations. The measurements, including those on the neutron-rich radioactive beams, have sufficient precision to distinguish between alternative models.

The E1 strength of exotic Ni isotopes has been measured at the R³B-LAND setup at GSI in Darmstadt. The experimental method relied on Coulomb excitation in inverse kinematics, for beam energies around 500 MeV/u. The excitation energy was reconstructed using the invariant mass, enabling the observation of the GDR and of additional low-lying E1 strength. The analysis of the neutron kinetic energies also allowed the extraction of the branching ratio for the direct neutron decay of ⁶⁸Ni, amounting to 25(2)%.

A recent Coulomb-excitation reorientation-effect measurement at TRIUMF has enabled information on diagonal matrix elements for the 3.368 MeV high-lying first excited state in ¹⁰Be from γ-ray data. The result allows for a comparison with state-of-the-art no-core-shell-model calculations and questions our knowledge of the spin-orbit interaction. Similar experiments using ¹²C beams at TRIUMF are aimed at measuring the diagonal matrix element for the first 2⁺ state at 4.439 MeV, which is currently determined as oblate, but presents an uncertainty of over 50%. Nuclear clustering effects are also being investigated using ²⁰Ne beams at iThemba LABS—the first ‘safe’ reorientation-effect measurement with ²⁰Ne beams. In addition, the occurrence of oblate shapes and shape coexistence will also be studied using ⁷⁰Se beams at 5.5 MeV/u at HIE-ISOLDE. These studies will shed light on nuclear shapes and resolved some of the timely shape conundra found in nuclei.