Background: Neutron-rich nuclei around neutron number N = 60 show a dramatic shape transition from spherical ground states to prolate deformation in 98 Sr and heavier nuclei. Purpose: The purpose of this study is to investigate the single-particle structure approaching the shape transitional region. Method: The level structures of neutron-rich 93,94,95 Sr were studied via the 2 H( 94,95,96 Sr, t ) one-neutron stripping reactions at TRIUMF using a beam energy of 5.5 AMeV. γ -rays emitted from excited states and recoiling charged particles were detected by using the TIGRESS and SHARC arrays, respectively. States were identified by gating on the excitation energy and, if possible, the coincident γ radiation. Results: Triton angular distributions for the reactions populating states in ejectile nuclei 93,94,95 Sr were compared with distorted wave Born approximation calculations to assign and revise spin and parity quantum numbers and extract spectroscopic factors. The results were compared with shell-model calculations and the reverse (d, p) reactions and good agreement was obtained. Conclusions: The results for the 2 H( 94 Sr, t ) 93 Sr and 2 H( 95 Sr, t ) 94 Sr reactions are in good agreement with shellmodel calculations. A two-level mixing analysis for the 0 + states in 94 Sr suggest strong mixing of two shapes. For the 2 H( 96 Sr, t ) 95 Sr reaction the agreement with the shell-model is less good. The configuration of the ground state of 96 Sr is already more complex than predicted, and therefore indications for the shape transition can already be observed before N = 60.

Background: The region around neutron number N = 60 in the neutron-rich Sr and Zr nuclei is one of the most dramatic examples of a ground state shape transition from (near) spherical below N = 60 to strongly deformed shapes in the heavier isotopes.Purpose: The single-particle structure of 95−97 Sr approaching the ground state shape transition at 98 Sr has been investigated via single-neutron transfer reactions using the (d, p) reaction in inverse kinematics. These reactions selectively populate states with a large overlap of the projectile ground state coupled to a neutron in a single-particle orbital.Method: Radioactive 94,95,96 Sr nuclei with energies of 5.5 AMeV were used to bombard a CD2 target. Recoiling light charged particles and γ rays were detected using a quasi-4π silicon strip detector array and a 12 element Ge array. The excitation energy of states populated was reconstructed employing the missing mass method combined with γ-ray tagging and differential cross sections for final states were extracted.Results: A reaction model analysis of the angular distributions allowed for firm spin assignments to be made for the low-lying 352, 556 and 681 keV excited states in 95 Sr and a constraint has been placed on the spin of the higher-lying 1666 keV state. Angular distributions have been extracted for 10 states populated in the d( 95 Sr, p) 96 Sr reaction, and constraints have been provided for the spins and parities of several final states. Additionally, the 0, 167 and 522 keV states in 97 Sr were populated through the d( 96 Sr, p) reaction. Spectroscopic factors for all three reactions were extracted. Conclusions:Results are compared to shell model calculations in several model spaces and the structure of low-lying states in 94 Sr and 95 Sr is well-described. The spectroscopic strength of the 0 + and 2 + states in 96 Sr is significantly more fragmented than predicted. The spectroscopic factors for the d( 96 Sr, p) 97 Sr reaction suggest that the two lowest lying excited states have significant overlap with the weakly deformed ground state of 96 Sr, but the ground state of 97 Sr has a different structure. * Corresponding author: wimmer@phys.s.u-tokyo.ac.jp arranging the nucleons in certain ways across the valence orbitals, which in turn causes a departure from sphericity [1]. The expense of such re-arrangements is dependent on the size of the energy gaps between single-particle orbitals above the Fermi energy. If the energy spacing is small, the valence nucleons can scatter into valence orbitals which are above the Fermi energy and drive the nucleus into a low-energy deformed configuration. On the other hand, if the energy spacing is large, the valence nucleons are unable to scatter into higher orbitals and this favors spherical shapes. The size of these energy gaps is in turn dependent on the number of valence nucleons, due to the monopole component of the residual

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The low energy excited 0 + 2,3 states in 96 Sr are amongst the most prominent examples of shape coexistence across the nuclear landscape. In this work, the neutron [2s 1/2 ] 2 content of the 0 + 1,2,3 states in 96 Sr was determined by means of the d( 95 Sr,p) transfer reaction at the TRIUMF-ISAC2 facility using the SHARC and TIGRESS arrays. Spectroscopic factors of 0.19(3) and 0.22 (3) were extracted for the 96 Sr ground and 1229 keV 0 + states, respectively, by fitting the experimental angular distributions to DWBA reaction model calculations. A detailed analysis of the γ-decay of the isomeric 0 + 3 state was used to determine a spectroscopic factor of 0.33(13). The experimental results are compared to shell model calculations, which predict negligible spectroscopic strength for the excited 0 + states in 96 Sr. The strengths of the excited 0 + 2,3 states were also analyzed within a two-level mixing model and are consistent with a mixing strength of a 2 =0.40(14) and a difference in intrinsic deformations of |∆β| = 0.31(3). These results suggest coexistence of three different configurations in 96 Sr and strong shape mixing of the two excited 0 + states.

The off-line ion source (OLIS) terminal consists of a microwave cusp ion source, either a surface ion source or a hybrid surface-arc discharge ion source and an electrostatic switch that allows selecting any one of the sources without mechanical intervention. These sources provide variety of beams to ISAC experiments, for commissioning the accelerators, for setting up the radioactive experiments, and for tuning the beam lines. The microwave ion source has been operational since 1995 and provides singly and doubly charged beams from various stable isotopes for many ISAC experiments at high and low energy areas. Originally its prime goal was to provide beams from gaseous elements, but later two ovens and a sputtering system were added in order to provide beams from liquids and from solids. The surface ion source installed in 2002 can provide low energy spread beams from alkali and semialkali elements. It also has three separate ovens and an ionizer. Therefore, it can provide three different temperature regions simultaneously to provide different beams to ISAC. It is mainly used for laser spectroscopy experiments and other experiments, which require a finite beam quality. A hybrid surface-arc discharge ion source was also developed and installed in order to meet specific demands from experiments. This source terminal is now automated for start up and for mass selection. It is capable of providing stable beams for months without maintenance and it is also capable of providing negative ion beams if required. To date, over 40 different isotopes including many rear isotopes were delivered to various experiments from the OLIS source terminal. Performances of the ion sources and some of the results are discussed.