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Three experiments based on the nuclear reactions 14N + 110Pd, 10B + 114Cd and 11B + 114Cd were performed. Coincidences between γ-rays emitted from these reactions were measured with the same detection array which consisted of 14 HPGe detectors. A new band structure was identified using an offline analysis of coincidence data. Because of the isomeric nature of the bandhead, the new band cannot be connected to any known state in any residual nuclei of the used reactions. To assign it to a specific nucleus, we evaluated the experimental population intensities of various known bands in known residual nuclei and investigated the entrance channel effects in the three different experiments. The population intensity patterns of the known bands were observed to exhibit regular systematics. Based on such experimental systematics, we suggest that the most reasonable nuclide assignment for the new band is the 120I nucleus.

Large areas of $$^{3}$$ He neutron detector array and corresponding readout electronics are used in the MPI built at China Spallation Neutron Source (CSNS) to measure the position and flight time of scattered neutrons, and MPI has a high requirement for the position resolution of $$^{3}$$ He neutron detector. A $$^{3}$$ He neutron detector readout electronics prototype composed of two front-end boards and one digital readout board is designed to meet the above requirements. Testing the whole readout electronics system before its mass production to ensure it can run correctly and fulfill the functional and performance requirements. The test of the readout electronics prototype is implemented in the laboratory, and a signal generator is used to generate electronic signals instead of actual neutron signals. The position resolution test of the readout electronics prototype with $$^{3}$$ He tubes is carried out in the No. 20 beamline measurement room of CSNS. The functional and performance tests in the laboratory state that the readout electronics prototype can fulfill the readout requirements. The typical value of charge resolution is 0.85 fC; the integral nonlinearity of charge is 0.094 $$\%$$ in the input charge range from 100 to 800 fC. The position resolution test result of the prototype with $$^{3}$$ He tubes is better than the design requirement of 10 mm and also quite good compared with that of some other commercial products. These tests provide a reliable basis for the mass production of the readout electronics prototype.

Excited states of 113In have been populated through the heavy-ion fusion evaporation reaction 110Pd(7Li, 4n)113In. A new band with the configuration of a proton d5/2 orbital is identified. Two ΔI = 2 intruder bands, built on the πh11/2 and the πg7/2 orbitals, have been extended to spins (63/2−ħ and (55/2+)ħ, respectively. The negative-parity πh11/2 intruder band shows a smooth increase in aligned spin, which is attributed to a strong proton-neutron interaction. The properties of the positive-parity πg7/2 band are discussed based on tilted axis cranking model calculations, and the features of the antimagnetic rotation for this band are shown after backbend. Furthermore, the contributions of the two-shears-like mechanism, the neutron (gd)ν shell and the core rotation are investigated for the positive-parity πg7/2 band.

Lifetimes of the 2 $$_1^{+}$$ , 4 $$_1^{+}$$ , 7 $$_2^{-}$$ , 10 $$_2^{+}$$ , 12 $$_2^{+}$$ , and 14 $$_1^{+}$$ states in $$^{138}$$ Nd populated via the $$^{123}$$ Sb( $$^{19}$$ F, 4n) $$^{138}$$ Nd fusion–evaporation reaction were measured with the recoil distance Doppler shift technique in combination with the differential decay curve method. The $$B(E2; 2_{1}^{+} \rightarrow 0_{1}^{+})$$ value fit well with the systematic trend in the Nd isotope chain and Grodzins rule, which proved that $$^{138}$$ Nd is a transitional nucleus.

The LaBr3(Ce) detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency. However, it has a relatively high intrinsic background radiation because of the naturally occurring radioisotopes in lanthanum, actinium, and their daughter nuclei. This limits its applications in low-counting rate experiments. In this study, we identified the radioactive isotopes in the $$\phi 3''\times 3''$$ Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system. Moreover, we carried out a Geant4 simulation of the experimental spectra to evaluate the activities of the main internal radiation components. The total activity of the background radiation of B380 is determined to be 1.523 (34) Bq/cm3. The main sources include 138La at 1.428 (34) Bq/cm3, 207Tl at 0.0135 (13) Bq/cm3, 211Bi at 0.0136 (15) Bq/cm3, 215Po at 0.0135 (3) Bq/cm3, 219Rn at 0.0125 (12) Bq/cm3, 223Fr at 0.0019 (11) Bq/cm3, 223Ra at 0.0127 (10) Bq/cm3, 227Th at 0.0158 (22) Bq/cm3, and 227Ac at 0.0135 (13) Bq/cm3. Of these, the activities of 207Tl, 211Po, 215Po, 223Fr, and 227Ac are deduced for the first time from the secular equilibrium established in the decay chain of 227Ac.

The GEM-based neutron detector has flourished in the past decade. However, most of the GEM-based neutron detectors operate in the flow-gas mode, and the long-term performances of the detectors may be unstable due to the dynamic changes of atmospheric pressure and ambient temperature. In this work, a sealed ceramic GEM-based neutron detector with 100 mm × 100 mm sensitive area was developed at China Spallation Neutron Source (CSNS). Various characteristics of the detector were determined. These included the plateau curve, neutron beam profile, neutron wavelength spectrum, spatial resolution (FWHM: 2.77 ± 0.01(stat) mm), two-dimensional (2D) imaging ability, neutron detection efficiency and long-term counting rate instability (Relative Standard Deviation (RSD): 0.80%). The results revealed the good performance of the detector in sealed mode. Furthermore, the detector can be used for measurements of the direct neutron beam at CSNS.

Excited states in the odd-A nucleus 71Ga have been studied via the 70Zn(7Li, )71Ga fusion-evaporation reaction with incident beam energies of 30 and 35 MeV. The level scheme is established up to spin = (29/2+) and an excitation energy 6.6 MeV. A previously known sequence built on the 9/2+ state is extended as a novel rotational band originating from the alignment. Furthermore, a negative-parity sequence is also reported. The observed energy levels of 71Ga have been interpreted in the framework of the nuclear shell model (SM).

The heavy ion fusion–evaporation reaction study for the high-spin spectroscopy of 75As has been performed via the reaction channel 70Zn(9Be, 1p3n)75As at a beam energy of 42 MeV. The collective structure especially a dipole band in 75As is established for the first time. The properties of this dipole band are investigated in terms of the self-consistent tilted axis cranking covariant density functional theory. Based on the theoretical description and the examination of the angular momentum components, this dipole band can be interpreted as a novel stapler band, where the valence neutrons in ( 1 g 9 / 2 ) orbital rather than the collective core are responsible for the closing of the stapler of angular momentum.

The lifetime of the state in Cd populated via the Zr ( O, 4n) Cd reaction has been measured with the Recoil Distance Doppler Shift technique in combination with the Differential Decay Curve Method. By subtracting the contamination in the data, the mean lifetime of the =2 633 keV state was determined as 9.9 (12) ps. The value calculated in this study is in good agreement with the experimental systematics and was compared to the shell model calculations.

High-spin states of 109Ag have been studied using the 7Li + 110Pd reaction at a beam energy of 46 MeV. A new negative-parity band decaying to the ground-state band by several new linking transitions is established. Meanwhile, seven new E2 crossover transitions of this band are observed, thereby confirming the spin-parity assignment and ordering of the dipole transitions above the Iπ = 19/2- level. A low energy γ-ray transition of 88 keV is found and placed at the bottom of the negative-parity band, and thus the Iπ = 17/2- level is tentatively assigned as the lowest observed state of this band. Experimental excitation energies and total angular momenta of the negative-parity band are compared with the predictions of self-consistent titled axis cranking relativistic mean-field theory with a three-quasiparticle configuration of πg9/2 -1 νh11/2(g7/2/d5/2)-1. Based on the theoretical description and the analyses of the angular momentum coupling, this negative-parity dipole band is suggested as a ``stapler'' band. By investigating the angular momentum components, it is found that the valence nucleons in the low-j orbitals play an active role in the ``stapler'' mechanism.

Excited states of the odd–odd nucleus 74 As have been investigated via heavy ion fusion evaporation reaction Zn 70 ( Li 7 , 3 n ) As 74 at beam energy of 30 MeV. The properties of the positive- and the negative- parity bands can be interpreted in terms of the Cranked Nilsson–Strutinsky (CNS) model calculations which show that the observed bands are built on the triaxial deformed shape. The inversion of the favored and unfavored signature branches observed in the positive-parity bands presents at high spins rather than normal signature inversion occurs at low spins. This phenomenon may be explained as the origin of unpaired band crossing in a highly rotating triaxial nucleus.

High-spin states in 161Er have been studied experimentally using the 150Nd(16O, 5n) reaction at a beam energy of 86 MeV. The relatively enhanced E1 transitions between the 5/2+[642] and 3/2−[521] bands are observed in 161Er, and the B(E1) values are extracted experimentally. The systematics of the R(E1) values in the N = 93 isotones are presented. It is found that the strength of the E1 transitions obviously exhibits angular momentum dependence, and the occurrence of the relatively enhanced E1 transitions could be attributed to octupole softness.

Ion dynamics in non-perfect quadrupole traps differ from those in a pure quadrupole field. We obtain an analytic expression for a quadrupole field superimposed with weak, higher-order multipole fields. Single ion dynamics in such trapping fields close to the instability point are investigated. We show that for an in-phase octopole field, oscillating envelopes of the axial displacement grow exponentially with the parameter deviation; whereas for an out-of-phase octopole field the growth of the oscillating envelopes follows a square-root law. A hard-sphere scattering model is assumed to incorporate collisions with buffer-gas molecules. The collision frequency and cross-section are defined. A simulation algorithm for many-ion dynamics is developed based on the Verlet algorithm and Monte Carlo techniques. We show how a weak octopole field affects the mass resolution in a significant way.

The effects of internal molecular fluctuations on chemical oscillations and chaos are investigated using a lattice-gas model for the dynamics of spatially distributed reacting systems. For limit cycle oscillations, the manner in which temporal correlations develop long-range order as the system size increases is studied. For chaotic attractors the correlation functions indicate the existence of noisy periodic behavior for global concentration variables. These features are explored for the three-variable autocatalator model. The effects of fluctuations on transverse front instabilities in the cubic autocatalysis reaction are also studied. The front instability is investigated in the lattice-gas model, and fluctuations are shown to lead to diffusive roughening of the front below the instability point and, in addition, to modify the cellular structure above the instability point.

Our studies on noise-induced transitions and projected dynamics in bistable chemical reactions are reviewed. We show that the noise-induced barrier crossing rates are determined by the time-dependent rate kernels that evolve according to projected dynamics. The rate kernels behave differently for projected and ordinary dynamics when barrier-crossing processes are fast. The validity of a phenomenological rate law description is discussed and rate coefficients for some chemically reacting systems are computed.

The effects of internal noise on chaotic and periodic dynamics of a chemical system are investigated. Calculations are carried out for a mesoscopic model of the Williamowski-R\"ossler reaction, a mass-action model that displays deterministic chemical chaos. The model incorporates internal fluctuations that arise from the reactive and diffusion processes in the system. The character of noisy dynamics is analyzed and questions related to the validity of deterministic models in the chaotic regime are discussed. The interplay among spatial degrees of freedom, system size, and internal fluctuations are studied for this chaotic dynamical system.

The onset of chemical turbulence in the 2‐D complex Ginzburg–Landau equation is studied for a class of finite‐amplitude, inhomogeneous, random initial conditions. Numerical simulations on a coupled map lattice corresponding to this reaction–diffusion equation are carried out in order to characterize the nature of the turbulent state. The phase diagram giving the zone of chemical turbulence in the parameter space that specifies the initial condition is determined numerically and compared with an analytical estimate.

High-spin states in 86Sr have been investigated by using in-beam γ ray spectroscopy with the 82Se(9Be, 5n)86Sr reaction at a beam energy of 53 MeV. A new dipole sequence has been observed and the mixed configurations of unpaired valence nucleons and before the alignment and the configuration after the alignment are assigned respectively. Shell-model and self-consistent titled axis cranking relativistic mean-field model calculations are performed to interpret the rotational structure and the characteristic features of magnetic rotation have been presented for the sequence.

High spin states of the odd-A 87Sr were populated by the fusion-evaporation reaction 82Se(9Be,4n) 87Sr at a beam energy of 46 MeV. Excited levels of 87Sr have been extended up to an excitation energy of 7.4 MeV at spin 31/2ħ. The coupling of a g9/2 neutron hole to the yrast states of the 88Sr core can account for the low-lying states in 87Sr. The structure of the higher spin states is discussed by analogy with those of the neighboring odd-A N = 49 isotones and possible configurations are proposed.

The recoil distance Doppler shift method has been widely used in the study of nuclear structure to determine the level lifetime and absolute transition probabilities. A capacitance servo control plunger based on this method has been successfully developed by the Nuclear Structure Group of the China Institute of Atomic Energy. Three microscopes were employed to check the parallelism and can therefore guarantee a delicate measurement of the distance between the target and the stopper. This new plunger made a successful performance in the test experiment and the measured lifetime of the 2 + →0 + transition in 78 Kr is in agreement with the previous value.

186Pt was tested in the framework of IBM-1 and the X(3) model. The results show that 186Pt is located close to the shape phase transition point, but the B(E2) values little agree with the X(3) model. The shape evolution in the yrast states of 186Pt is also discussed in detail. TRS calculation exhibits a flat bottomed potential at low spin states, but a relatively deep minimum at high spin states. It suggests that a shape evolution from vibrational mode to rotational mode happens in 186Pt. The result is in agreement with the E-GOS calculation.

High spin states of 128La have been studied through the fusion-evaporation reaction 118Sn(14N, 4n)128La at a beam energy of 69 MeV. A positive-parity side band with the same configuration as that of the yrast band has been identified. Moreover, it is noted that the energy separation ΔE(I) = E(I)side − E(I)yrast of all doublet bands reported in odd-odd nuclei in the A~130 mass region exhibit a staggering pattern systematically, and they stagger up at even-spin and stagger down at odd-spin.

The low energy neutral excitations of incompressible fractional quantum Hall states are called collective modes or magnetic excitons. This work develops techniques for computing their dispersion at general filling fractions for reasonably large systems. New structure is revealed; in particular, the collective mode at 1/3 is found to possess several minima, with the energy of the principal minimum significantly smaller than the earlier estimate. \pacs{73.40.Hm, 73.20.Dx, 73.20.Mf}, Comment: 4 pages, 3 postscript figures

Excited states of the odd-odd nucleus 122I are investigated via the fusion-evaporation reaction 116Cd(11B,5n) at a beam energy of 68 MeV. The two most strongly populated bands in 122I are observed up to excitation energies around 10.5 MeV. Their possible configurations at lower spins are assigned to πh11/2 ⊗ vh11/2 and πh11/2 ⊗ vd5/2 based on the observed population, B(M1)/B(E2) values, alignments and signature splitting. E1 transitions are observed connecting the πh11/2 ⊗ vd5/2 band to the πh11/2 ⊗ vh11/2 band, which may be evidence of octupole collectivity. Band terminations caused by the full alignment of the valence nucleons outside the 114Sn core are observed in both bands.

Gamma rays with energies between 80 keV and 1500 keV produced by 133Ba and 152Eu standard sources are measured with the clover detector. Relative efficiencies and add-back factors are determined in both crystals and full clover modes. The add-back characteristics have been calculated using Monte-Carlo simulation code Geant4. The simulation and measurements agree very well.

In order to investigate the evolution of X(5) in rotating 178Os, an experiment populating 178Os via the fusion evaporation reaction 154Sm(29Si,5n)178Os was performed at the HI-13 tandem accelerator at the China Institute of Atomic Energy (CIAE). Lifetimes of excited states above 8+ in the yrast band in 178Os have been measured using the Doppler shift attenuation method. Lifetimes above 12+ states were measured for the first time. The deduced transitional quadruple moments (Qt), together with the previous data using the recoil distance Doppler shift (RDDS) method are compared with theoretical calculations based on the X(5) model and the interaction Boson model (IBM). Above the 10+ states, the Qt values fit well with the X(5) predictions. The present result suggests that the shape of a nucleus 178Os keeps X(5) critical point symmetry as spin increases to at least 14+. The shape change of 178Os with spin increasing is similar to that of 176Os.

Vortex core dynamics is studied in the Brusselator both near to and far from the Hopf bifurcation line for random and pair initial conditions. Extensive simulations are carried out for a pair of counter‐rotating vortices close to the Hopf bifurcation line. Provided the vortices are not so far apart that wave‐front annihilation produces strong gradients between their centers, the simulation results compare favorably with theories based on the complex Ginzburg–Landau equation. Far from the Hopf line the vortex core dynamics changes character and phenomena such as periodic motion of the vortex centers arise.

By means of beam chopping and ? - ? concidence technique, the in-beam ?-rays and decay ?-rays of the 150 MeV 40Ca+58Ni reaction products have been measured. The four strongest transition ?-rays of 92Rh have been clearly observed. The decay ?-rays of 92Rh have been identified for the first time. The spin and parity of 6+ are tentatively assigned to the ground state of 92Rh. Part of the decay scheme of 92Rh is proposed.

High-spin states in 190Tl have been studied via the 160Gd(35Cl, 5nγ) reaction. The level scheme, consisting of the πh9/2⊗vi13/2 oblate band and a cascade with character of single particle excitations, has been established. Spin values have been firmly assigned to the oblate band in 190Tl, resulting in low-spin signature inversion in the πh9/2⊗vi13/2 oblate band for the first time. Based on the similarity of the level structure in doubly odd Tl nuclei, spin values for the oblate bands in 192–200Tl should be re-assigned, and a consistent low-spin signature inversion has occurred in these oblate deformed nuclei. The low-spin signature inversion phenomena can be interpreted qualitatively by using the 2-quasiparticle plus rotor model including p-n residual interactions.

JOURNAL ARTICLE, info:eu-repo/semantics/published

JOURNAL ARTICLE, info:eu-repo/semantics/published

We study a theoretical model that describes an optically pumped Fabry–Perot cavity filled with sodium vapor as a nonlinear absorptive medium. The nonlinear medium is subjected to a static magnetic field. A difference of population is built up between Zeeman sublevels of the ground state when the pump exceeds a threshold. This gives rise to a nonsymmetrical absorption of the two circularly polarized components of the incident light. The emphasis of this paper is on the derivation of analytic results. We show that the system can exhibit a self-pulsing behavior and that in a suitable domain of parameters the system has two or more steady states. This is known as optical bistability or optical multistability.

When second-harmonic generation is realized in a passive cavity, self-pulsing occurs beyond a critical threshold. We analyze the vicinity of this threshold when the input field is amplitude modulated at twice the self-pushing frequency. We determine analytically the domain of stable synchronous response.

We study a model of a far-infrared laser that was recently shown to explain a number of experimental results adequately. In a systematic way we perform linear stability analyses analytically. This determines up to four bifurcation diagrams in steady state, two of which are rather exceptional: In one case the whole branch of finite intensity is unstable, in the second case the low-intensity domain of the finite steady state is unstable. In both these cases the laser displays periodic or chaotic output without ever reaching a stable steady output.

We present a theoretical study of a multilongitudinal-mode laser with an intracavity-doubling crystal. The longitudinal modes are coupled to one another through frequency-doubling processes (because of the crystal) and through sum-frequency processes (because of the laser cavity). This leads to a mode–mode competition that significantly alters the nature of the output solutions.

We study the process of second-harmonic generation when the nonlinear crystal is in an active laser cavity. This system is characterized by isolated bifurcations (steady and Hopf) but also by interacting bifurcations. They are studied both analytically and numerically.