Radiative capture of fast neutrons by 89Y and 140Ce

The γ-ray spectra from the reactions ⁸⁹Y(n, γ)⁹⁰Y and ¹⁴⁰Ce(n, γ)¹⁴¹Ce have been measured in the neutron energy range of 6.2–15.6 MeV. The pulse-height spectra were recorded with NaI(Tl) spectrometers and time-of-flight techniques were used to improve signal-to-background ratio. Capture cross sections were determined for γ-ray transitions to the two $\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels at 0 and 203 keV of ⁹⁰Y and to the $\text{2}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ ground state of ¹⁴¹Ce as well as integrated cross sections to bound states in these nuclei. The observed γ-ray spectra and partial radiative capture cross sections were compared with predictions of the direct-semidirect capture theory. The resonance behaviour with neutron energy of both the ground-state and integrated partial capture cross sections shows the validity of the semidirect model for ⁸⁹Y and ¹⁴⁰Ce in the region of neutron energy encompassing the giant-dipole resonance. The observed symmetry of the cross sections about the peak of the resonance argues strongly for the complex form of the particle-vibration coupling interaction. A detailed comparison of the predictions of the DSD model using the complex coupling interaction shows that the capture cross sections are relatively insensitive to the real part of the interaction.     

The γ-decay of excited states of 141Ce observed in the 140Ce(d,pγ) reaction

The reaction ¹⁴⁰Ce(d, pγ)¹⁴¹Ce was studied at 8 MeV bombarding energy. Protons and γ-rays were detected in coincidence. The decay scheme is deduced, and the branching ratios are compared to the results of other experiments and to model calculations.     

Studies of single-neutron holes in the transitional nuclei N = 83–89: The 142Ce(d,t)141Ce and 142Ce(3He, α)141Ce pick-up reactions

The level structure of ¹⁴¹Ce up to 3.7 MeV excitation energy has been investigated by the (d, t) and (³He, α) reactions using 17 MeV deuteron and 24 MeV ³He beams respectively. The angular distributions have been analyzed with standard DWBA calculations and spectroscopic factors are deduced. The experimental information is compared to unified model calculations involving both one-particle and two-particle one-hole configurations with quadrupole and octupole vibrations of the underlying N = 82 and N = 84 core.     

Radiative β-decay in 141Ce

The spectral distribution of the continuous gamma radiation accompanying non-unique first forbidden β-decay of 32 d ¹⁴¹Ce has been measured in the energy range 200–560 KeV with a 4.5 cm × 5.08 cm NaI(T1) scintillation spectrometer. The source electrons were eliminated using an elctromagnet. The raw spectrum was corrected for pile-up, finite energy resolution, Compton electron distribution and geometrical γ-detection efficiency using the method of Liden and Starfelt. The corrected distribution is compared with the direct and detour theories of Lewis and Ford, and Ford and Martin, respectively. Total disagreement between experiment and theory was observed over the entire region of the investigated spectrum. In the energy region from 200 to 350 keV, however, the measured spectrum lies between the direct and detour theories.     

VAMPIR calculations for 128Ba and 130Ce: Two mechanisms of backbending

Hartree-Fock-Bogoliubov calculations with spin and number projection before the variation (VAMPIR) are performed for the nuclei ¹²⁸Ba and ¹³⁰Ce using a slightly renormalized Brueckner G-matrix as effective interaction in a rather large single-particle basis. The results are compared to those of Hartree-Fock-Bogoliubov calculations with projection after the variation, those of multiconfiguration calculations (MONSTER) and to experiment. In both nuclei the VAMPIR and the MONSTER approaches turn out to be of about the same quality and agree rather well with the experimental data. Analysis of the VAMPIR mean fields reveals that two somewhat different mechanisms are responsible for the backbending observed in the yrast bands of the two nuclei. While in ¹³⁰Ce the well-known alignment of two high-j quasiparticles (proton $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$) is found, in ¹²⁸Ba first a neutron pair is scattered from the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ to the $\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ orbit, and then the larger alignment energy of the less occupied neutron $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ states produces the backbend. This latter effect is in agreement with the predictions of a simple model presented by us some years ago.     

Magnetic moments at backbending and spectroscopy of 134Ce

Employing the static hyperfine fields at cerium nuclei in magnetized Fe and Gd hosts, the g-factor of the ¹³⁴Ce(10⁺) state at backbending (E_{x = 3719.3 keV}) has been determined as g = ? 0.30 (25). The coexistence of this neutron-dominated state with the ($\text{v}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{n}}\text{10}{}^{\mathrm{+}}$ isomer (E_x = 3208.5 keV, g = ?0.19(1)) is unexpected. A comprehensive spectroscopic study following the ¹²²Sn(¹⁶O, 4n) reaction, including γ-angular distributions, prompt and delayed γ coincidence and recoil-distance measurements has yielded new information on quasi-collective bands of both parities. The properties of the low-lying positive-parity states are well described by the interacting boson model.     

M1 and E2 transitions in 59Ni

Employing the Kuo-Brown interaction, M1 and E2 transition rates for the low-lying levels of ⁵⁹Ni are calculated and the results are found to be in reasonably good agreement with the observed values.     

Neutron hole states in 138La and 140Pr

Protons accelerated to 30 MeV were used to investigate low-lying states in the odd-odd nuclei ¹³⁸La and ¹⁴⁰Pr with (p, d) reactions. The elastic scattering of 30 MeV protons and 23 MeV deuterons was also studied to determine optical potentials. Experimental angular distributions are compared with distorted-wave Born approximation calculations to extract spin, parity, and spectroscopic factors for levels up to 432 keV of excitation in ¹⁴⁰Pr and 530 keV in ¹³⁸La. Comparisons with the simple shell-model predictions and extended shell-model calculations are presented. The ¹⁴⁰Pr levels appear experimentally to have an almost pure particle-hole structure whereas the ¹³⁸La levels exhibit substantial mixing.     

In-beam study of 136Ce and 138Nd isotones with N = 78

Excited states in ¹³⁶Ce and ¹³⁸Nd have been investigated by means of in-beam spectroscopy with the (p, 4nγ) reaction. Excitation functions and angular distributions of γ-rays were measured with a Ge(Li) detector, and conversion electron spectra were taken with a magnetic spectrometer. Time-dependent spectra of γ-rays revealed delayed components with half-lives of 2.2μsec and 0.41μsec in ¹³⁶Ce and ¹³⁸Nd, respectively. Most of the excited states are classified as belonging to the quasi-ground-state rotational band and the quasi-gamma band. Negative parity 5^? and 7^? states were also observed.     

An estimate of the hindrance factors for γ-ray transitions near the neutron binding energy from the reaction 143Nd(n, γα)140Ce

The reaction ¹⁴³Nd(n, γα)¹⁴⁰Ce has been investigated at the 55.3 eV resonance. A theoretical analysis has been carried out, yielding lower limits for the hindrance factors of γ-ray transitions between highly excited states close to the neutron binding energy. Some evidence for the predominance of M1 transitions in this energy region was found.     

Experimental generalized oscillator strengths of the 61S0→61P1-excitation of barium

Experimental generalized oscillator strengths f(K²) for excitations of the 6¹P₁ state of Ba, measured at 200 eV and 300 eV, are compared with theoretical data obtained by Kim and Bagus. Theoretical and experimental data agree at K² < 0.3 a.u., but differ significantly at greater K².     

Distribution of single-particle strengths in the nuclei 207Tl, 207Pb, 209Bi and 209Pb

Within the theory of finite Fermi systems we calculate the distribution of single-particle strengths in the odd mass nuclei surrounding ²⁰⁸Pb. The Dyson equation with an energy dependent mass operator is solved and the resulting single-particle propagator is analysed. It turns out that the concept of quasiparticles used in this theory is very well justified for nearly all the states in the first and the second shells below and above the Fermi surface.     

Regarding the 21S0 and 23S1 multiplets

<正>This paper discusses the masses and possible members of 2¹S₀ and 2³S₁ meson multiplets in the framework of meson-meson mixing and Regge phenomenology.For the 2¹S₀ meson nonet,K^*（1460） may be the observed state of the 2¹S₀ isodoublet with a mass of 1400 MeV and the mass ofω（1420） is 1412 MeV.For the 2³S₁ meson nonet,K^*（1410） seems too light to be the 2³S₁ ns member.The fact that the agreement between the present findings and those given by experiments and other different approaches is satisfactory implies that the assignments in this paper may be reasonable.     

Electromagnetic transition strengths in 24Na

Mean lifetimes, excitation energies and branching ratios of ²⁴Na states, populated in the ²³Na(d, p)²⁴Na reaction have been measured. Gamma-ray spectra were measured at three angles in coincidence with proton groups at θ_p = 169°. Mean lifetimes obtained from DSA are (excitation energy in keV, lifetime in fs): 563, > 1000; 1341, 95 ± 30; 1344, 38 ± 11; 1346, > 1500; 1512, 38 ± 11; 1846, 260 ± 50; 1885, 36 ± 9; 2513, 15 ± 7; 2563, < 25; 2904, 50 ± 15; 2978, < 25; 3216, 22 ± 8; 3372, 19 ± 5. For higher levels up to 4207 keV upper limits of 30 fs were set. In combination with earlier work the following unique spin(-parity) assignments could be made: J^π(1846) = 2⁺, J(2513) = 3, J^π(3745) = 3^?. A new level at E_x = 3681.7 ± 0.6 keV is reported.     

Low-lying levels of 140Pr

The doubly odd nucleus ¹⁴⁰Pr has been investigated by means of the ¹⁴¹Pr(d, t)¹⁴⁰Pr and ¹⁴⁰Ce(p, nγ)¹⁴⁰Pr reactions. Twenty-eight levels, up to 1300 keV excitation, were observed in the pickup study. DWBA analysis was used to determine l-values and spectroscopic factors for all but a few which are very weakly populated. Gamma-ray angular distributions, measured at E_p = 4.78 MeV for the five strongest γ-rays, show appreciable nuclear alignment and demonstrate the feasibility of such experiments in this mass region. Taken together, the two studies have permitted the identification of the 12 levels expected from the low-lying ($\text{π2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν2}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$), ($\text{π2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν3}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$), ($\text{π1}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{ν2}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$) and (π1g_{$\text{7}\text{2}$}ν3s_{$\text{1}\text{2}$}^?1) configurations. Tenta assignments for the strong odd-parity states are suggested on the basis of their spectroscopic factors.     

Mixing between the 23S1 and 13D1Ds

Mixing between the 23S1 and 13D1Ds is studied within the 3P0 model. If mixing between these two 1 states exists, Ds1* （2700） ± and DsJ*（2860）± could be interpreted as the two orthogonal mixed states with mixing angle θ≈-80 °in the case of a special β for each meson. However, in the case of a universal β for all mesons, D_s1^*（2700） ± could be interpreted as the mixed state of 23S1 and 13D1 with mixing angle 12° < θ < 21° but D_sJ^*（2860）± seems difficult to interpret as the orthogonal partner of D_s1^*（2700）±.     

Alpha-particle strengths from the 16O(6Li,d)20Ne reaction

The ¹⁶O(⁶Li, d)²⁰Ne reaction has been studied at bombarding energies of 20, 32 and 38 MeV. The α-particle spectroscopic strengths have been extracted for levels up to 12.15 MeV in excitation. Nondirect processes appear to contribute significantly to all levels at 20 MeV and to high spin levels (6⁺ and 8⁺) at 32 MeV. Strengths extracted for members of the ground state band assuming (sd)⁴ transfer are unequal at both 32 and 38 MeV, in marked contrast to theoretical predictions. To explain this, particle-hole correlations in ¹⁶O(g.s.), inelastic channel coupling in the reaction and perhaps other effects as well, have to be considered. Strengths extracted for members of excited bands and α-decay reduced widths compare poorly with each other and with simple SU(3) predictions.     

The 54Fe(p, d)53Fe and 140Ced(p, d)139Ce reactions at 122 MeVag

The ⁵⁴Fe($\text{p}$, d)⁵³Fe and ¹⁴⁰Ce($\text{p}$, d)¹³⁹Ce reactions have been studied at a proton energy of 122 MeV. Analyzing powers and angular distributions were obtained for outgoing deuterons to the strong low-lying single-particle states in both nuclei. These data along with the data of others at 26, 29, 41, 52 and 24, 35, 55 MeV for ⁵⁴Fe and ¹⁴⁰Ce respectively, have been compared with exact-finite-range DWBA calculations carried out in a consistent fashion to determine the energy dependence of the spectroscopic factors. A strong energy dependence was noticed for the spectroscopic factors when the l-values were large.     

Oscillator strengths for 2 ^2P-n ^2D transitions of lithium-like systems with Z=11 to 20

The dipole-length, velocity and acceleration absorption oscillator strengths for the 1s^22p－1s^2nd(3≤n≤9) transitions of the lithium-like systems with Z=11 to 20 are calculated using the energies and the multiconfiguration interaction wavefunctions obtained from a full core plus correlation method. The agreement between the f-values calculated from the length, velocity and acceleration formulae is excellent. Our results agree closely with the experimental data available in the literature. Combining these discrete oscillator strengths with the single-channel quantum defect theory, the discrete oscillator strengths for the transitions from 1s^22p state to highly excited states (n≥10) and the oscillator strength densities corresponding to the bound-free transitions are obtained.     

Neutron-hole strengths and isobaric analog states in 95Zr

The ⁹⁶Zr(τ, α)⁹⁵Zr reaction at 39 MeV incident energy was used to populate both the low-lying and highly excited (up to an excitation energy of 18 MeV) analog states in ⁹⁵Zr and some low-lying levels in other Zr isotopes. The main components of the 2d_{$\text{5}\text{2}$}. and 1g_{$\text{9}\text{2}$}. hole strengths and the analogs of the 2p_{$\text{1}\text{2}$}., 2p_{$\text{3}\text{2}$}. and 1f_{$\text{3}\text{2}$}. proton hole states in ⁹⁵Y have been observed in this work. Angular distributions of transitions to 27 levels in ⁹⁵Zr have been extracted and analysed with DWBA calculations to yield spectroscopic factors. Between the excitation energies of 1 and 3 MeV in ⁹⁵Zr a number of levels with l = 2, 4 and 5 angular distributions have been identified. These are associated with the 2d_{$\text{3}\text{2}$}, 1g_{$\text{7}\text{2}$} and 1h_{$\text{11}\text{2}$} components already observed in the previous study of the ⁹⁴Zr(d, p) and (α, τ) reactions. The total strength and center of gravity for levels assigned to the (1g_{$\text{9}\text{2}$})^?1 configurations in ⁹⁵Zr are presented and compared to the results obtained from the studies of neutron pick-up reaction on ⁹¹Zr and ⁹⁸Mo. For the isobaric analog states observed between the excitation energies of 15 and 17 MeV, total widths, Coulomb displacement energies and spectroscopic factors are also determined from this experiment and the results compared with the properties of the low-lying proton hole states in the ⁹⁵Y parent nucleus.