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Many-body localization (MBL) describes a quantum phase where an isolated interacting system subject to sufficient disorder displays non-ergodic behavior, evading thermal equilibrium that occurs under its own dynamics. Previously, the thermalization-MBL transition has been largely characterized with the growth of disorder. Here, we explore a new axis, reporting on an energy resolved MBL transition using a 19-qubit programmable superconducting processor, which enables precise control and flexibility of both disorder strength and initial state preparations. We observe that the onset of localization occurs at different disorder strengths, with distinguishable energy scales, by measuring time-evolved observables and many-body wavefunctions related quantities. Our results open avenues for the experimental exploration of many-body mobility edges in MBL systems, whose existence is widely debated due to system size finiteness, and where exact simulations in classical computers become unfeasible., Comment: 9 pages, 5 figures + supplementary information

We present a new experimental method for measuring inner-shell ionization cross sections of low-charged ions colliding with hydrogen gas target in a storage ring. The method is based on a calibration by the well-known differential cross sections of proton elastic scattering on nuclei. K-shell ionization cross section of 1047(100) barn for the 95 MeV/u 58Ni19+ ions colliding with hydrogen atoms was obtained in this work. Compared to the measured ionization cross section, a good agreement is achieved with the prediction by the Relativistic Ionization CODE Modified program (RICODE-M).

High Intensity heavy-ion Accelerator Facility (HIAF) project is being constructed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). An in-flight High energy FRagment Separator (HFRS) at HIAF was designed to study the properties of rare isotopes far away from the line of beta stability and their involved nuclear reactions of astrophysics interests. HFRS is a two-stage magnetic system which consists of Pre-Separator and Main-Separator. The maximum magnetic rigidity of 25 Tm was designed in particular for experiments with very neutron-rich rare isotopes beams and studies of hypernuclei and Δ-resonances in exotic nuclei. A dispersive mode and an achromatic mode were designed for different experimental requirements. The HFRS device can be used to separate and purify the rare isotopes produced by the projectile fragmentation of all primary beams up to Uranium or by the projectile fission of Uranium ions via Bρ-ΔE-Bρ method. The detailed HFRS ion-optical design including the first order and the higher order, and the magnet specification were presented in this paper.

Recent numerical and experimental works have revealed a disorder-free many-body localization (MBL) in an interacting system subjecting to a linear potential, known as the Stark MBL. The conventional MBL, induced by disorder, has been widely studied by using quantum simulations based on superconducting circuits. Here, we consider the Stark MBL in two types of superconducting circuits, i.e., the 1D array of superconducting qubits, and the circuit where non-local interactions between qubits are mediated by a resonator bus. We calculate the entanglement entropy and participate entropy of the highly-excited eigenstates, and obtain the lower bound of the critical linear potential $\gamma_{c}$, using the finite-size scaling collapse. Moreover, we study the non-equilibrium properties of the Stark MBL. In particular, we observe an anomalous relaxation of the imbalance, dominated by the power-law decay $t^{-\xi}$. The exponent $\xi$ satisfies $\xi\propto|\gamma-\gamma_{c}|^{\nu}$ when $\gamma, Comment: 9+7 pages, 10+7 figures, 2 tables

7 pags., 4 figs., 1 tab., Available experimental neutron skin thicknesses of even-even stable Ca, Ni, Sn, Pb, and Cd isotopes are evaluated, and separate trends of neutron skin thickness versus relative neutron excess δ=(N-Z)/A are observed for different isotopic chains. This phenomenon is quantitatively reproduced by the deformed Skyrme Hartree-Fock + Bardeen-Cooper-Schrieffer model with SLy4 force., This work is supported in part by the NSFC (12022504, 11775273, U1932140,12121005), by the CAS Pioneer Hundred Talents Program, by the CAS Open Research Project of large research infrastructures, by the CAS Maintenance and Reform of Large Research Infrastructures (DSS-WXGZ2018-0002), and by the Max Plank Society. Y.A.L. acknowledges the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 682841 “ASTRUm”) and P.S. acknowledges MCI/AEI/FEDER, UE (Spain) (Grant no. PGC2018-093636-B-I00)

We experimentally study the ergodic dynamics of a 1D array of 12 superconducting qubits with a transverse field, and identify the regimes of strong and weak thermalization with different initial states. We observe convergence of the local observable to its thermal expectation value in the strong-thermalizaion regime. For weak thermalization, the dynamics of local observable exhibits an oscillation around the thermal value, which can only be attained by the time average. We also demonstrate that the entanglement entropy and concurrence can characterize the regimes of strong and weak thermalization. Our work provides an essential step towards a generic understanding of thermalization in quantum systems., Comment: 6+6 pages, 4+8 figures

Two new excited bands built on the πh11/2 configuration have been identified in Nd135 in addition to the known πh11/2 band. The energy spectra of the excited bands and the available electromagnetic transition probabilities are in good agreement with theoretical results obtained using quasiparticle-plus-triaxial-rotor model calculations. The properties of the bands identify them as tilted precession bands instead of wobbling bands. Our results give a new insight into the interpretation of the low-lying bands in odd-A mass nuclei, and can stimulate future studies to address the nuclear triaxiality.

Quantum information scrambling under the dynamics of a closed many-body system is of wide interest. The tripartite mutual information (TMI) can quantify the scrambling via its stable negative value under temporal evolution. Here, we study the quench dynamics of the TMI in a nonintegrable Ising model with different initial states in the regimes of strong and weak thermalization. Our numerical results show that the most efficient scrambling can occur when the inverse temperatures of initial states are near zero and in the regime of strong thermalization, and weak thermalization accompanies slow scrambling. We then present an experimental protocol for observing strong and weak thermalization in a one-dimensional array of superconducting qubits, based on which the relation between scrambling and the degree of thermalization revealed in this work can be directly verified by superconducting quantum simulators. The inevitable decoherence effects in real situations are also analyzed, paving the way for faithful quantum simulations on actual experimental platforms.

The authors present a method of charactering many-body localization transition via the quench dynamics of diagonal entropy, as an experimentally feasible quantity. The critical point of many-body localization transition can be efficiently detected. The adopted scaling ansatz respects the Harris-Luck bound, and the scaling exponent can provide information for the universality class of many-body localization transition.

Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11Be on a 208Pb target at an incident energy of 140 MeV (about 3.5 times the Coulomb barrier) were measured at HIRFL-RIBLL. A strong suppression of the Coulomb nuclear interference peak is observed in the measured quasielastic scattering angular distribution. The result demonstrates for the first time the persistence of the strong breakup coupling effect reported so far for reaction systems involving neutron-halo nuclei at this relatively high incident energy. The measured quasielastic scattering cross sections are satisfactorily reproduced by continuum discretized coupled channel (CDCC) calculations as well as by the XCDCC calculations where the deformation of the 10Be core is taken into account. The angular and energy distributions of the 10Be fragments could also be well reproduced considering elastic breakup (CDCC and XCDCC) plus nonelastic breakup contributions, with the latter evaluated with the model by Ichimura, Austern and Vincent [1]. The comparison of the 10Be energy distributions with simple kinematical estimates evidence the presence of a significant post-acceleration effect which, in the (X)CDCC frameworks, is accounted for by continuum-continuum couplings. National Key Research and Development Program of China (Grant No. 2018YFA0404403) National Natural Science Foundation of China (Grant No. 11775013, No. 11947203, No. 11575256, and No. U1632138) Youth Innovation Promotion Association CAS (No. 2020411) Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-P European Union’s Horizon 2020 (Grant Agreement No. 654002)

Superconducting simulators are used to investigate dynamical phase transitions, revealing their applications in quantum metrology., Nonequilibrium quantum many-body systems, which are difficult to study via classical computation, have attracted wide interest. Quantum simulation can provide insights into these problems. Here, using a programmable quantum simulator with 16 all-to-all connected superconducting qubits, we investigate the dynamical phase transition in the Lipkin-Meshkov-Glick model with a quenched transverse field. Clear signatures of dynamical phase transitions, merging different concepts of dynamical criticality, are observed by measuring the nonequilibrium order parameter, nonlocal correlations, and the Loschmidt echo. Moreover, near the dynamical critical point, we obtain a spin squeezing of −7.0 ± 0.8 dB, showing multipartite entanglement, useful for measurements with precision fivefold beyond the standard quantum limit. On the basis of the capability of entangling qubits simultaneously and the accurate single-shot readout of multiqubit states, this superconducting quantum simulator can be used to study other problems in nonequilibrium quantum many-body systems, such as thermalization, many-body localization, and emergent phenomena in periodically driven systems.

The very first in-ring reaction experiment at the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), namely proton elastic scattering on stable $^{58}\mathrm{Ni}$ nuclei, is presented. The circulating $^{58}\mathrm{Ni}^{19+}$ ions with an energy of 95 MeV/u were interacting repeatedly with an internal hydrogen gas target in the experimental storage ring (CSRe). Low-energy proton recoils from the elastic collisions were measured with an ultra-high vacuum compatible silicon-strip detector. Deduced differential cross sections were normalized by measuring $k$-shell x rays from $^{58}\mathrm{Ni}^{19+}$ projectiles due to the $^{58}\mathrm{Ni}^{19+}\text{\ensuremath{-}}{\mathrm{H}}_{2}$ ionization collisions. Compared to the experimental cross sections, a good agreement has been achieved with the theoretical predictions in the measured region, which were obtained by using the global phenomenological optical model potentials. Our results enable new research opportunities for optical model potential studies on exotic nuclides by using the in-ring reaction setup at the HIRFL-CSR facility.

The cross section for one-proton knockout from $^{16}\mathrm{C}$ with a large neutron-proton separation energy asymmetry on a carbon target has been measured at an intermediate beam energy of around 240 MeV/nucleon. The measured cross section is compared to the predictions based on the eikonal reaction model with shell-model structure inputs. The beam-energy dependence of the reduction on the extracted spectroscopic strength for strongly bound nucleon removal is derived from combining the existing intermediate-energy data with the present measurement. The deduced reduction factor ${R}_{s}$, defined as the ratio of the measured and theoretical cross sections, for the strongly bound nucleon removal at around 240 MeV/nucleon is consistent with the systematics observed from knockout reactions induced by light nuclear targets at intermediate energies of around 80 MeV/nucleon.

Quantum coherence and correlation of thermal states in the extended XY spin chain are studied in terms of the recently proposed l 1 norm, skew information, and Bures distance of geometry discord (BGD), respectively. The entanglement measured via concurrence is calculated for reference. A two-dimensional susceptibility is introduced to explore their capability in highlighting the critical lines associated with quantum phase transitions in the model. It is shown that the susceptibility of the skew information and BGD is a genuine indicator of quantum phase transitions, and characterizes the factorization. However, the l 1 norm is trivial for the factorization. An explicit scaling law of BGD is captured at low temperature in the XY model. In contrast to the entanglement, quantum coherence reveals a kind of long-range nonclassical correlation. Moreover, the obvious relation among model parameters is extracted for the factorized line in the extended model. Those are instructive for the understanding of quantum coherence and correlation in the theory of quantum information, and quantum phase transitions and factorization in condensed-matter physics.

We use a two-dimensional electrostatic model to explore Van der Pauw (VdP) method on samples with holes. Results of electrostatic simulation based on the model are consistent with the experimental results. The quantitative investigation of VdP method on sample with one hole indicate the value of f, i.e. the right hand side of VdP equation, is depend on the position of contacts and the size of holes. We also quantitatively explore the VdP method used on sample with two holes in special position of contacts and sample geometry. According to the guidance of simulation and experiment, we find proper position of contacts, which make VdP equation f = 1 valid again on sample with holes. It is helpful for the optimization of VdP method and measuring the resistivity of sample with holes.

The cross sections for two-neutron removal from $^{15,16}\mathrm{C}$ on a carbon target have been measured at around 240 MeV/nucleon. The measured cross section for $^{15}\mathrm{C}$ is smaller than for $^{16}\mathrm{C}$. The trends of the cross sections for $^{15,16}\mathrm{C}$ are inconsistent with the previously reported experimental data, but in agreement with the theoretical predictions based on eikonal-model calculations. Based on the present results of $^{15,16}\mathrm{C}$ combined with the available experimental data on $^{17--20}\mathrm{C}$, an odd-even staggering of the two-neutron removal cross sections along the neutron-rich carbon isotopic chain from $^{15}\mathrm{C}$ to $^{20}\mathrm{C}$ is observed, and this feature is well reproduced by the theoretical calculations.

We study the quench dynamics of entanglement spectra in the Kitaev chain with variable-range pairing quantified by power-law decay rate $\alpha$. Considering the post-quench Hamiltonians with flat bands, we demonstrate that the presence of entanglement-spectrum crossings during its dynamics is able to characterize the topological phase transitions (TPTs) in both short-range ($\alpha$ > 1) or long-range ($\alpha$ < 1) sector. Properties of entanglement-spectrum dynamics are revealed for the quench protocols in the long-range sector or with $\alpha$ as the quench parameter. In particular, when the lowest upper-half entanglement-spectrum value of the initial Hamiltonian is smaller than the final one, the TPTs can also be diagnosed by the difference between the lowest two upper-half entanglement-spectrum values if the halfway winding number is not equal to that of the initial Hamiltonian. Moreover, we discuss the stability of characterizing the TPTs via entanglement-spectrum crossings against energy dispersion in the long-range model., Comment: 8 pages, 6 figures

The out-of-time-order correlators (OTOCs) is used to study the quantum phase transitions (QPTs) between the normal phase and the superradiant phase in the Rabi and few-body Dicke models with large frequency ratio of theatomic level splitting to the single-mode electromagnetic radiation field frequency. The focus is on the OTOC thermally averaged with infinite temperature, which is an experimentally feasible quantity. It is shown that thecritical points can be identified by long-time averaging of the OTOC via observing its local minimum behavior. More importantly, the scaling laws of the OTOC for QPTs are revealed by studying the experimentally accessible conditions with finite frequency ratio and finite number of atoms in the studied models. The critical exponents extracted from the scaling laws of OTOC indicate that the QPTs in the Rabi and Dicke models belong to the same universality class., 9 pages, 10 figures, v3: published version added; v2: supplemental material added, more results added

Quantifying quantum coherence has attracted considerable interests. In the present work, we employ two measures of quantum coherence recently proposed in terms of the skew information and the trace norm, respectively, to investigate the quantum phase transitions (QPTs), factorization in the XY model and the thermal phase transitions (TPTs) in the transverse field Ising model. Two quantifications of quantum nonlocality via the same distance measure of the quantum coherence are also studied for reference. It is shown that two types of quantum coherence are reliable in identifying QPTs and TPTs. However, only the quantum coherence based on the skew information can detect factorization. In addition, the quantum coherence and nonlocality measured via the same distance space have similar finite temperature scaling law, while the quantum coherence based on skew information and trace norm has different finite temperature scaling law. Moreover, the skew-information-based quantum coherence at finite temperature suggests that factorization vanishes when temperature exceeds 0.02 (Boltzmann constant $$k_{B} = 1$$ ), which is in agreement with the results of the fidelity for states with different distances of spin-pairs.

The present paper describes the development of in-ring reaction measurements at the Cooler-Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). A Silicon (Si) detector has been developed with cost-efficient methods to meet the requirements of Ultra-High Vacuum (UHV) conditions in a storage ring. The UHV-Si detector and luminosity monitor Si(Li) detector were installed at the experimental cooler storage ring (CSRe). The pilot in-ring reaction experiment about proton elastic scattering on 58Ni 19 + ions has been operated successfully with the basic detector system in inverse kinematics , which opens an opportunity for in-ring reaction measurements at the HIRFL-CSR. This is an important step towards realizing in-ring reaction measurements with large Si detector arrays at the next generation High Intensity heavy ion Accelerator Facility (HIAF).

We investigate the diagonal entropy for ground states of the extended Kitaev chains with extensive pairing and hopping terms. The systems contain rich topological phases equivalently represented by topological invariant winding numbers and Majorana zero modes. Both the finite size scaling law and block scaling law of the diagonal entropy are studied, which indicates that the diagonal entropy demonstrates volume effect. The parameter of volume term is regarded as the diagonal entropy density, which can identify the critical points of symmetry-protected topological phase transitions efficiently in the studied models, even for those with higher winding numbers. The formulation of block scaling law and the capability of diagonal entropy density in detecting topological phase transitions are independent of the chosen bases. In order to manifest the advantage of diagonal entropy, we also calculate the global entanglement, which cannot show clear signatures of the topological phase transitions. This work provides a new quantum-informatic approach to characterize the feature of the topologically ordered states and may motivate a deep understanding of the quantum coherence and diagonal entropy in various condensed matter systems.

Local and intrinsic quantum coherence, as two contributions of total quantum coherence, have been introduced by Radhakrishnan et al. [C. Radhakrishnan, M. Parthasarathy, S. Jambulingam, and T. Byrnes, Phys. Rev. Lett. 116, 150504 (2016)]. In the present work we study the property of local, intrinsic, and total quantum coherence in critical systems such as the $XY$ model, extended $XY$ model, and Ashkin-Teller model to analyze their capability in identifying the second-order, infinite-order quantum phase transitions, as well as the topological quantum phase transitions. It is shown that not only the total coherence, but also the local and intrinsic coherence can spotlight the critical points efficiently. Moreover, the long-range properties of total and local coherence, and the short-range properties of intrinsic coherence are analyzed. The total and local coherence for spin-pairs farther than nearest neighbors can highlight the critical points while the intrinsic coherence is absent for long-distance spin-pairs.

We investigate the diagonal entropy(DE) of the ground state for quantum many-body systems, including the XY model and the Ising model with next nearest neighbour interactions. We focus on the DE of a subsystem of L continuous spins. We show that the DE in many-body systems, regardless of integrability, can be represented as a volume term plus a logarithmic correction and a constant offset. Quantum phase transition points can be explicitly identified by the three coefficients thereof. Besides, by combining entanglement entropy and the relative entropy of quantum coherence, as two celebrated representatives of quantumness, we simply obtain the DE, which naturally has the potential to reveal the information of quantumness. More importantly, the DE is concerning only the diagonal form of the ground state reduced density matrix, making it feasible to measure in real experiments, and therefore it has immediate applications in demonstrating quantum supremacy on state-of-the-art quantum simulators., Comment: 8 pages, 7 figures

Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional gamma-ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I = 19/2 states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population following the projectile fragmentation of 78Kr at energies of 480A MeV on a beryllium target. The 19/2 state isomeric ratios of 53Fe produced from different projectiles in the literature have also been extracted as a function of mass number difference between projectile and fragment (mass loss). The results are compared to ABRABLA07 model calculations. The isomeric ratios of 53Fe produced using different projectiles suggest that the theory underestimates not only the previously reported dependence on the spin but also the dependence on the mass loss., Comment: 6 pages, 5 figures

Spectroscopic information has been extracted on the hole-states of 55Ni, the least known of the quartet of nuclei (55Ni, 57Ni, 55Co and 57Co), one neutron away from 56Ni, the N=Z=28 double magic nucleus. Using the 1H(56Ni,d)55Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f7/2, p3/2 and the s1/2 hole-states of 55Ni. This new data provides a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to reproduce the excitation energies and spectroscopic factors of the s1/2 hole state below Fermi energy.

Fragment yields of projectile fragmentation reactions using primary beams of 36,40Ar at 50 MeV/nucleon on 64 Ni target have been measured. Fragment yields of different isotopes were obtained for Z ≥ 5 in RIBLL fragment seperator. We compare the extracted yields to the predictions of the empirical parametrization of fragmentation cross-sections(EPAX) and Statistical Abration-Ablation model(SAA) considering the RIBLL separator transmission rate. Isotope yield ratios between these 2 reactions were calculated, isoscaling parameters α and β, their dependence on fragment atomic number Z and neutron number N were calculated.

The longitudinal momentum distributions of $^{7}\mathrm{Be}$ fragments in the breakup of $^{8}\mathrm{B}$ on a carbon target have been measured at 36 MeV/u. The different mechanisms have been distinguished by coincidence measurements. The longitudinal momentum distributions of $^{7}\mathrm{Be}$ fragments from both the stripping and the diffraction mechanisms are consistent with the results of noneikonal calculations and CDCC calculations. The full widths at half maximum of the longitudinal momentum distributions are $124\ifmmode\pm\else\textpm\fi{}17$ and $92\ifmmode\pm\else\textpm\fi{}7$ MeV/$c$ for the stripping and diffraction components, respectively. The comparison with the different model calculations is discussed. It is crucial to separate the different reaction mechanisms experimentally to benchmark nuclear reaction theories.

A fragment separator, the Radioactive Ion Beam Line in Lanzhou, has been constructed at the Heavy Ion Research Facility of Lanzhou and in operation since January 1998. In this paper, the features of the structure and performance are described in detail. Some early stage results are presented also.

Strong odd-even staggering (OES) of the yields of fragments, produced by fragmenting Kr78 projectiles, has been measured by employing the combination of an in-flight fragment separator and a storage ring. It is shown that the OES of fragment yields of Tz=−1/2 and Tz=1/2 mirror nuclei critically depends on both pairing and shell structure, especially at the closed shells Z=20 and 28. A comparison of the relative OES of yields and of particle-emission threshold energies reveals unambiguously that the origin of the OES of fragment yields is mainly determined by the OES of the particle-emission threshold energies, which contain both pairing and shell effects.

Physics letters / B 735, 327 - 331 (2014). doi:10.1016/j.physletb.2014.06.046, Published by North-Holland Publ., Amsterdam

To improve the effective interactions in the $pf$ shell, it is important to measure the single-particle and single-hole states near the $N$ $=$ 28 shell gap. In this paper, the neutron spectroscopic factors of hole states from the unstable neutron-rich ${}^{45}$Ar ($Z$ $=$ 18,$N$ $=$ 27) nucleus have been studied using the ${}^{1}$H(${}^{46}$Ar,$d$) ${}^{45}$Ar transfer reaction in inverse kinematics. Comparison of our results with the particle states of ${}^{45}$Ar produced in ${}^{2}$H(${}^{44}$Ar, $p$) ${}^{45}$Ar reaction shows that the two reactions populate states with different angular momenta. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of ${}^{45}$Ar. These are the ground state (${f}_{7/2}$), the first-excited state (${p}_{3/2}$), and the ${s}_{1/2}$ and ${d}_{3/2}$ states. While large basis shell-model predictions describe spectroscopic properties of the ground and ${p}_{3/2}$ states very well, they fail to describe the ${s}_{1/2}$ and ${d}_{3/2}$ hole states.

The projectile fragmentation reactions of ${}^{40}$Ar at 57 MeV/nucleon on ${}^{9}$Be and ${}^{181}$Ta targets have been studied by the Radioactive Ion Beam Line in Lanzhou (RIBLL) at the Heavy-Ion Research Facility in Lanzhou (HIRFL). The momentum distributions of fragments have been measured and the competition between different mechanisms are observed. The production cross sections have been obtained and compared with the empirical parametrization of fragmentation cross section (EPAX), abrasion-ablation (AA), and heavy-ion phase space exploration (HIPSE) models, and the target dependence of fragment cross sections has also been discussed.

The ultraviolet optical transition of the isomeric state in 229Th has attracted much attention recently due to its potential application to building an atomic/nuclear clock with ultra-high precision. However, the lowest nuclear excitation energy and the lifetime of the first excited state of 229Th were not measured directly and precisely until now, and how to precisely determine this isomer state of the 229Th is an urgent requirement. Here an experimental approach of using a technique similar to that of dielectronic recombination to measure the transition energy of the isomer state of 229Th at heavy ion storage rings is described. It is expected that the resonant transition can be found and determined with a precision better than several milli-eV.

The breakup reactions of Cl-31 + C-12 at 44A MeV are investigated experimentally. The longitudinal momentum distribution of S-30 after one-proton removal from Cl-31 has been obtained. By assuming core plus a valence proton structure, the momentum distribution is studied using the few-body Glauber model. The calculation shows that the width of momentum distribution for a valence proton with l = 2 is consistent with the experimental data, which indicates a dominant d-wave component for the valence proton in Cl-31.

Mass excesses of short-lived $A=2Z\ensuremath{-}1$ nuclei $^{63}\mathrm{Ge}$, $^{65}\mathrm{As}$, $^{67}\mathrm{Se}$, and $^{71}\mathrm{Kr}$ have been directly measured to be $\ensuremath{-}46\text{ }921(37)$, $\ensuremath{-}46\text{ }937(85)$, $\ensuremath{-}46\text{ }580(67)$, and $\ensuremath{-}46\text{ }320(141)\text{ }\text{ }\mathrm{keV}$, respectively. The deduced proton separation energy of $\ensuremath{-}90(85)\text{ }\text{ }\mathrm{keV}$ for $^{65}\mathrm{As}$ shows that this nucleus is only slightly proton unbound. X-ray burst model calculations with the new mass excess of $^{65}\mathrm{As}$ suggest that the majority of the reaction flow passes through $^{64}\mathrm{Ge}$ via proton capture, indicating that $^{64}\mathrm{Ge}$ is not a significant $rp$-process waiting point.

Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich Ar-34 and neutron-rich Ar-46 beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between Ar-34 and Ar-46. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of Ca40-49 isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.

Two-{alpha} emission from high-lying excited states of {sup 18}Ne was studied by complete-kinematics measurements. The {sup 18}Ne beam at the energy of 51.8 MeV/u was bombarding a {sup 197}Au target to populate the excited states via Coulomb excitation. Products of two-{alpha} emission, {sup 10}C-{alpha}-{alpha}, were measured by an array of silicon strip detectors and a CsI + PIN telescope. With the help of Monte Carlo simulations, the experimental results show the characteristics of sequential two-{alpha} emission via {sup 14}O excited states. Sequential two-{alpha} and two-proton emissions from {sup 18}Ne via one-particle daughter states are compared and the distinction of the opening angles of these two modes originates from the difference of the mass ratio of emitted particles to daughter nuclei.

An experiment to study exotic two-proton emission from excited levels of the odd-$Z$ nucleus $^{28}\mathrm{P}$ was performed at the National Laboratory of Heavy Ion Research-Radioactive Ion Beam Line (HIRFL-RIBLL) facility. The projectile $^{28}\mathrm{P}$ at the energy of $46.5$ MeV/$u$ was bombarding a $^{197}\mathrm{Au}$ target to populate the excited states via Coulomb excitation. Complete-kinematics measurements were realized by the array of silicon strip detectors and the $\mathrm{CsI}+\mathrm{PIN}$ telescope. Two-proton events were selected and the relativistic-kinematics reconstruction was carried out. The spectrum of relative momentum and opening angle between two protons was deduced from Monte Carlo simulations. Experimental results show that two-proton emission from $^{28}\mathrm{P}$ excited states less than $17.0$ MeV is mainly two-body sequential emission or three-body simultaneous decay in phase space. The present simulations cannot distinguish these two decay modes. No obvious diproton emission was found.

Spectroscopic factors have been extracted for proton rich 34Ar and neutron rich 46Ar using the (p,d) neutron transfer reaction. The experimental results show little reduction of the ground state neutron spectroscopic factor of the proton rich nucleus 34Ar compared to that of 46Ar. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions but inconsistent with the trends observed in knockout reaction measurements., Comment: 11 pages, 2 figures. submitted to PRL

Collisions involving 112Sn and 124Sn nuclei have been simulated with the improved Quantum Molecular Dynamics transport model. The results of the calculations reproduce isospin diffusion data from two different observables and the ratios of neutron and proton spectra. By comparing these data to calculations performed over a range of symmetry energies at saturation density and different representations of the density dependence of the symmetry energy, constraints on the density dependence of the symmetry energy at sub-normal density are obtained. Results from present work are compared to constraints put forward in other recent analysis., Comment: 8 pages, 4 figures,accepted for publication in Phy. Rev. Lett

An experiment of a $^{29}\mathrm{S}$ beam bombarding a $^{197}\mathrm{Au}$ target at an energy of 49.2 MeV/u has been performed to study the two-proton correlated emission from $^{29}\mathrm{S}$ excited states. Complete-kinematics measurements were carried out in the experiment. The relative momentum, opening angle, and relative energy of two protons, as well as the invariant mass of the final system, were deduced by relativistic-kinematics reconstruction. The $^{27}\mathrm{Si}$-$p\text{\ensuremath{-}}p$ coincident events were picked out under strict conditions and the phenomenon of $p\text{\ensuremath{-}}p$ correlations was observed among these events. The mechanisms of two-proton emission were analyzed in a simple schematic model, in which the extreme decay modes like $^{2}\mathrm{He}$ cluster emission, three-body phase-space decay, and two-body sequential emission were taken into account. Associated with the Monte Carlo simulations, the present results show that two protons emitted from the excited states between 9.6 MeV and 10.4 MeV exhibit the features of $^{2}\mathrm{He}$ cluster decay with a branching ratio of ${29}_{\ensuremath{-}11}^{+10}%$.

The {beta}-decay of {sup 18}N has been studied using {beta}-n and {beta}-{gamma} coincidence methods. The {sup 18}N ions were produced by the fragmentation of the E/A=68.8 MeV {sup 22}Ne beam on a thick beryllium target. A newly constructed neutron detector system with wide energy detection range and low-energy detection threshold was used. The 619 {+-} 2 ms half-life of the {sup 18}N {beta}-decay was found to be in very good agreement with the previous measurements. Transitions to 11 {beta}-delayed neutron emitting states in {sup 18}O have been observed with a total branching ratio of 6.98 {+-} 1.46%. The Gamow-Teller {beta}-decay strengths of {sup 18}N to these levels were deduced and compared with the shell model calculations. The intensities of the strong {gamma}-ray transitions in {sup 18}O were found to be consistent with recent work.

Masses of neutron-deficient Ni-58 projectile fragments have been measured at the HIRFL-CSR facility in Lanzhou, China employing the isochronous mass spectrometry technique. Masses of a series of short-lived T-z = -3/2 nuclides including the Cr-45 nucleus have been measured with a relative uncertainty of about 10(-6)-10(-7). The new Cr-45 mass turned out to be essential for modeling the astrophysical rp-process. In particular, we find that the formation of the predicted Ca-Sc cycle in X-ray bursts can be excluded.