Level structure of 99Tc by inelastic scattering and proton stripping

The ⁹⁸Mo(³He, d)⁹⁹Tc and ⁹⁹Tc(d, d') reactions have been used to study the levels of of ⁹⁹Tc. Spin-parity assignments are made for nearly all states below 1.5 MeV excitation. Strong j-dependence is noted for l = 1 transitions in the proton stripping reaction, making possible several new spin assignments. The inelastic scattering data on ⁹⁹Tc are compared to similar data on ⁹⁸Mo, and are found to be in agreement with a coupling scheme based on a shell model with good seniority.     

Level structure of 47Ti from the (d,p) reaction in 46Ti

The reaction ⁴⁶Ti(d, p) is studied at 10 MeV using the Aldermaston tandem Van de Graaff accelerator and a multichannel magnetic spectrograph. A total of 180 levels are observed up to an excitation of ≈ 7.2 MeV and the stripping angular distributions are analysed in terms of the DWBA theory of direct reactions using the NL/FR optical model potential. Spins, parities and spectroscopic factors are deduced for various levels. Summed spectroscopic factors and quasiparticle energies are obtained for shell model states. Properties of low-lying levels in ⁴⁷Ti are compared with the MBZ and Coriolis coupling models and also with those of the isotonic nuclei ⁴⁵Ca and ⁴⁶Sc.     

Single-neutron transfer reactions 76, 78, 80, 82Se(p,d)75, 77, 79, 81Se at EP = 33MeV

Single-neutron transfer reactions on even-even Se nuclei have been studied using 33 MeV incident proton energy from the ANU cyclograaff facility. A total of 120 levels have been seen below 4 MeV excitation energy in ^{75, 77, 79, 81}Se isotopes. Angular distributions for 88 states were extracted and analysed with DWBA theory yielding a number of new l_n assignments. Coriolis coupling calculations have been carried out for low-level spin states in all four isotopes.     

Band crossings in 170Os

Excited states in the neutron-deficient nucleus ¹⁷⁰Os were identified up to spin (24⁺) in the yrast band and to spin (23⁻) in the lowest negative-parity band. Deformation systematics implied by the 2⁺ state energies for the very light osmium isotopes are compared with theory. Band-crossing frequencies, alignments and alignment gains are compared with cranked shell-model calculations. Deformation changes are required to obtain detailed agreement. A three-band mixing approach is invoked to explain the low-spin yrast anomaly in ¹⁷²Os and to reproduce the yrast band in ¹⁷⁰Os. The excitation energy of the postulated “intruder” band in ¹⁷⁰Os and ¹⁷²Os is deduced.     

High-spin yrast and non-yrast bands in 176Os, 178Os and 180Os

High-spin yrast and non-yrast states have been identified in ¹⁷⁶Os, ¹⁷⁸Os and ¹⁸⁰Os using (¹⁶O, xn) reactions, and γ-ray techniques. Band crossing anomalies are observed in each of the positive-parity yrast bands. The magnitude of these anomalies decreases with decreasing neutron number, an effect attributed to the change in the moment of inertia of the ground state rotational bands. A 23 ns isomer, predominantly K^π = 7^?, is identified at 1930 keV in ¹⁸⁰Os. The configuration of this isomer is discussed on the basis of the properties of its rotational band. Negative parity, odd and even spin, sideband sequences are observed in each isotope. Their relationship to rotation-aligned octupole and 2-quasiparticle bands is discussed from their excitation energies, band spacings, and decay properties. Detailed calculations for Coriolis mixed bands are carried out for the likely 2-quasiproton and 2-quasineutron configurations. An anomaly observed at spin 17 in the odd-spin negative-parity sequence in ¹⁸⁰Os is attributed to a band crossing with a fourquasiparticle configuration.     

Investigating highly excited states of the 8Li isotope

Highly excited states of the ⁸Li isotope are sought in absorption reactions of π^? mesons stopped by ^10,11B isotopes. The ground and three excited states of the ⁸Li isotope are observed in inclusive measurements of reactions ¹⁰B(π^?, d)X and ¹¹B(π^?, t)X. The states with excitation energies E _x ≈ 8.7 and 10.1 MeV are observed for the first time in correlation measurements of reactions ¹⁰B(π^?, dt)X and ¹¹B(π^?, tt)X.     

Excitation of 3−1, 5−1 and 7−1 states in Te isotopes A = 120, 122; 124, 126, 128 WITH (p,t) reactions

The reactions ^ATe(p, t)^A?2Te have been studied with even-A targets using 51.9 MeV protons. Three or more strongly excited triton peaks were observed in the spectra of the ^A-2Te nuclei at energies of ≈ 2–3 MeV excitation. Angular distributions are analyzed using DWBA theory. The lowest octupole (3^?₁) states of five Te isotopes are strongly excited. The lowest 3^? state in ¹²⁰Te is established at 2.09 ±0.02 MeV. The systematics of excitation energies and cross sections for the lowest 5^? and 7^? states are interpreted by a quasiparticle model.     

Nuclear levels in193Os

The previously completely unknown energy levels of¹⁹³Os have been investigated using the reactions¹⁹²Os(d, p)¹⁹³Os and¹⁹²Os(n, γ)¹⁹³Os. The neutron separation energy was measured to be 5583.5±2.0 keV. Most of the states below 500 keV can be qualitatively interpreted in terms of the Nilsson model; however the occurrence of four levels with significantl=1 transfer strength in this energy range is incompatible with that model. The Nilsson orbital systematics of the odd-A Os and W isotopes are compared.     

Temperature dependence of quantal and thermal dampings of the hot giant dipole resonance

A systematic study of the damping of the giant dipole resonance (GDR) in ⁹⁰Zr, ¹²⁰Sn and ²⁰⁸Pb as a function of temperature T is performed. The double-time Green function technique is employed to determine the single-particle and GDR dampings. The single-particle energies, obtained in the Woods-Saxon potential for these nuclei, are used in the calculations. The results show that the coupling of collective vibration to the pp and hh excitations, which causes the thermal damping width, is responsible for the enlargement of the total width with increasing temperature up to T ≈ 3MeV and its saturation at higher temperatures. The quantal width, which arises from the coupling of the collective mode to the ph excitations decreases slowly with increasing temperature. The effect of single-particle damping on the GDR width is small. The results are found in an overall agreement with the experimental data for the GDR width, obtained in the inelastic α scattering and heavy-ion fusion reactions at excitation energies E^* ⩽ 450 MeV. At high excitation energies (E^* > 400 MeV) a behavior similar to the transition from zero to ordinary sounds is observed.     

Nuclear levels and spectroscopy of191Os

Thirty-nine states, all except two of which are new, have been observed up to 1535 keV in¹⁹¹Os using the reactions¹⁹⁰Os(d,p)¹⁹¹Os,¹⁹²Os(d, t)¹⁹¹Os with 12 MeV deuterons and magnetic analysis with photographic emulsions of the outgoing particles, and¹⁹⁰Os(n, γ)¹⁹¹Os with thermal neutrons and three modes of gamma detection in the energy range from 40 keV to ～6 MeV. The neutron separation energy was determined as 5758.5±2.0 keV in agreement with the value of the (d, p) reaction. TheQ value for the (d, t) reaction was determined as ?1265±15 keV. Spins and parities are assigned for most of the states below 800 keV. The states below 463 keV are shown to be qualitatively but not quantitatively consistent with the expectations of the Nilsson model. Nilsson systematics of the 1/2^?: ¦510¦ and 3/2^? ¦512¦ orbitals in odd-A Os isotopes with increasing neutron number can be understood in terms of decreasing deformation. Anomalously large (d, p) and (d, t) cross sections populating 5/2^? and 3/2^? states at 134 and 142 keV, respectively, are explained as a tendency to restore the cross sections expected for a spherical nucleus. Evidence for triaxiality in¹⁹¹Os is observed in the form of a 5/2^? state at 273 keV which appears to be a rotational state built on the 9/2^? ground state.     

On the structure of two-quasiparticle states in even-A Xe isotopes

The excitation energies of proton and neutron two-quasiparticle states in even-A xenon isotopes are studied within the shell-model framework. The results suggest that in the lighter isotopes (A≦126) the proton excitations might be yrast, whereas in the heavier ones (A≧130) the neutron-hole excitations dominate at lower energies. This finding would then explain the complex excitation spectra found in^{126, 128, 130}Xe, where the two excitation modes occur at comparable energies.     

Description of the Pt and Os isotopes in the interacting boson model

Properties of the even-even Pt and Os isotopes are investigated in the framework of the interacting boson approximation, including the neutron-proton degree of freedom. It is shown that the transition between the gamma unstable region of the heavier Pt isotopes towards the more axially symmetric deformed festures of the lighter Os and Pt isotopes can be described very well by the IBA hamiltonian; qualitatively the properties of the transitional region are reproduced by the smooth change of one parameter, χ_ν, which determines the character of the quadrupole-quadrupole interaction. Calculated excitation energies and electromagnetic properties are compared with experiment.     

Two-nucleon pick-up from spin-12 targets (II). 89Y

The angular distributions for the ⁸⁹Y(p, t), (p, τ), and (d, α) reactions are compared to DWBA predictions and to the data for the ⁹⁰Zr(p, t) and (d, α) reactions. Several new spins are assigned to levels of ⁸⁷Y. A weak coupling model is tested by the comparison between the reactions on ⁸⁹Y and ⁹⁰Zr, and found to fail. The (d, α) reaction is found to populate strongly levels at excitation energies of 2.70 MeV and 3.07 MeV in ⁸⁷Sr, corresponding roughly in Q-value and strength to states formed in ths ⁸⁸Sr(d, α)⁸⁶Rb reaction.     

Untersuchung der Anregungen von186Re nach der (n, γ)-Reaktion

Prompt and delayedγ-γ-coincidences were measured after slow neutron capture in¹⁸⁵Re by use of Ge(Li)-detectors. New isomers were found at 99.4 keV (T_1/2=27±7ns) and at ≈330keV (T_1/2=17.4±0.7 ns). The evaluation of coincidence data established 10 rotational bands with band heads below 700 keV. The level scheme is discussed in detail: Nilsson assignments are proposed for the band configurations, and calculations of Coriolis mixing andγ-transition probabilities are presented which reproduce the experimental level energies and transition intensities very satisfactorily.     

Neutron-emission mechanisms in the <Superscript>115</Superscript>In(<Emphasis Type="Italic">α, xn</Emphasis>) reactions

Spectra and angular distributions of neutrons from the ¹¹⁵In(α, xn) reactions were measured at α-particle energies of 16, 18, 27, and 45 MeV. The measurements were performed with time-of-flight neutron spectrometers at pulsed accelerators of charged particles. The data obtained in this way were analyzed within the models of equilibrium, preequilibrium, and direct reaction mechanisms. The exact formalism of Hauser-Feshbach statistical theory was used in the calculations, level densities in residual nuclei excited in the reactions under consideration being found from the neutron evaporation spectra in the (p, n) reactions on tin isotopes. Contributions from equilibrium, preequilibrium, and direct neutron emission were studied in a wide range of α-particle energies.     

A high resolution study of 26Al via the (p,d) reaction

Excitation energies and angular distributions of ²⁶Al levels in the first 6 MeV of excitation have been measured with the ²⁷Al(p, d)²⁶Al reaction at E_p = 35 MeV. Deuteron spectra were analyzed with an Enge split-pole magnetic spectrograph and recorded on nuclear emulsions (experimental resolution ≈ 6 keV, FWHM); supplementary data were recorded with position-sensitive wire proportional counters. The angular distributions were analyzed with the DWBA to extract the l-values and associated spectroscopic factors of the neutron transfers. The results for excitation energies, l-values, spectroscopic factors, and values of J^π, T are discussed in terms of previous experimental and theoretical work and in the light of new shell-model calculations for this system.     

Shell-model calculations on Ni and Cu isotopes

Binding energies, excitation energies and spectroscopic factors have been calculated for^57–67Ni and^58–68Cu in an unrestricted (2p_3/2, lf _5/2,2p_1/2) shell-model space. The effective two-body matrix elements are obtained from the modified surface delta interaction (MSDI) and from a least-squares fit to experimental binding and excitation energies (ASDI). The average deviation between about 100 experimental and calculated energies is 0.14MeV for MSDI and 0.08 MeV for ASDI. Excitation energies of high-spin states are given also. Spectroscopic factors have been calculated for all single-nucleon transfer reactions on stable Ni or Cu targets leading to Ni or Cu isotopes. For spectroscopic factors larger than 0.4 the average deviation between theory and experiment is about 30%. The experimentally observed and calculated spectroscopic strengths are compared by using sum rules and are found to be consistent. An extensive compilation has been made of experimental data on energies,J ^π assignments and spectroscopic factors.     

Charge exchange and excitation cross sections at collisions of alpha particles with be-like impurity oxygen ions in a plasma

The charge exchange and excitation cross sections at collisions of alphas with O⁴⁺(1s ²2s ²) impurity atoms in a hot plasma for striking energies E _c varying from 20 keV to 2 MeV are determined for the first time. The cross sections are calculated using the method of close-coupling equations with 13 singlet four-electron quasi-molecular states taken as a basis. The partial cross sections of charge transfer to the 1s, 2s, and 2p states of a He⁺ ion and for O⁴⁺(1s ²2s ²) → O⁴⁺(1s ²2lnl’) (n = 2, 3) electronic excitation of an oxygen ion are found. The maximal value of the charge exchange total cross section roughly equals 2.2 × 10^?16 cm² at E _c ≈ 0.7 MeV. The excitation total cross section has a maximum of ≈ 7.7 × 10^?16 cm² at E _c ≈ 80 keV for single-electron excitation and ≈6.5 × 10^?16 cm² at E _c ≈ 0.7 MeV for two-electron excitation.