New multi-phonon gamma vibrational bands in A∼110 neutron-rich nuclei

The high spin states of neutron-rich ¹⁰³Nb, ¹⁰⁷Tc and ¹⁰⁹Tc nuclei in A～110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. In ¹⁰³Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In ¹⁰⁷Tc and ¹⁰⁹Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified. The two-phonon bands are first observed in odd-Z nuclei. The characteristics for these band structures have been discussed.     

Observations of “pairing-free” Kπ = 1+ rotational bands in deformed odd-odd A ∼ 100 nuclei

Rotational bands with K^π = 1⁺ in the odd-odd nuclei ^100,102₃₉Y and ^102,104₄₁Nb are postulated from β⁻ decay of t heir even-even parents. Each two-quasiparticle band has a moment of inertia very close to that of a rigid spheroidal nucleus with deformation β ∼ 0.3, hence these bands are nearly “pairing free”.     

Search for chiral bands in A ～ 110 neutron-rich nuclei

High spin states in A ～ 110 neutron-rich 106Mo, 110Ru and 112Ru nuclei have been reinvestigated by measuring the prompt γ-rays from the spontaneous fission of 252Cf. Two similar sets of bands are observed to high spins in each of three nuclei. Through analyzing of characters of the band structures, the chiral doublet bands are suggested in 106Mo, 110Ru and 112Ru.     

New multi-phonon gamma vibrational bands in A～110 neutron-rich nuclei

The high spin states of neutron-rich 103Nb, 107Tc and 109Tc nuclei in A~110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of 252Cf with the Gammasphere detector array. In 103Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In 107Tc and 109Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified...     

Analysis of the threshold anomaly in proton elastic scattering on A ∼- 30 mass nuclei

The threshold anomaly in energy-averaged excitation functions of proton elastic scattering on A ∼- 30 mass nuclei is analyzed in the framework of the Lane model for p-wave threshold effects. A quantitative correlation between the strength of the threshold anomaly and the 2p-wave neutron strength function is reported.     

Collective-pair structure of Kπ = 0+,1+,2+ bands in deformed nuclei

In the framework of the microscopic IBM the fermion pair structure for several collective excitations has been investigated. In this study the deformed nucleus ¹⁵⁶Gd is treated as an example. The theoretical method used consists of a combination of a triaxial Hartree-Fock-Bogoliubov method and a Hill-Wheeler method. We discuss the effects of keeping the structure of the collective S-, D- and G-pairs fixed as well as varying these structures. The combination of fixed S-, D-, and G-pairs with only one other set of S'-, D'- and G'-pairs is also investigated.     

Study of the potential energy of “octupole”-deformed nuclei in a multidimensional deformation space

The collective potential energy of even-even “octupule”-deformed nuclei is studied in a multidimensional deformation space in both radium and barium regions. This energy is calculated by the macroscopic-microscopic method, with the Yukawa-plus-exponential model taken for the macroscopic part and the Strutinski shell correction (based on the Woods-Saxon single-particle potential) used for the microscopic part of the energy. The deformations β_λ of all multipolarity degrees: λ = 2, 3, …, 7 (or even 8) are treated as independent variables. The multipolarities: λ = 5, 6 and 7, usually omitted or treated in an average way up to now, are found to be important for the properties of the nuclei.     

Study ofγ radiation from100Pd decay

This paper presents a study of the rays from the electron capture decay of 3.63d ¹⁰⁰Pd. Singles and coincidence measurements provided an accurate determination of-ray intensities and an improved knowledge of the¹⁰⁰Rh level scheme. Experimental evidence supports excitation of levels in¹⁰⁰Rh at 86-, 136- and 154 keV, not previously reported from the decay of¹⁰⁰Pd.On leave from Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires, Argentina     

Anharmonicities of γ-vibrations in deformed nuclei

The anharmonicities of γ-vibrations are studied within the multiphonon method in different even-even deformed nuclei where the first K^π = 2⁺ vibrational state appears well below the energy gap: ¹³⁰Ce, ^162–164Dy, ^164–168Er, ¹⁸⁶Os. The anharmonicities previously obtained in ¹⁶⁸Er appear to be a general property of these nuclei.     

Cross-correlations between low-γ nuclei in solids via a common dipolar bath

Correlation of chemical shifts of low-γ nuclei (such as 15N) is an important method for assignment of resonances in uniformly-labeled biological solids. Under static experimental conditions, an efficient mixing of low-γ nuclear spin magnetization can be achieved by a thermal contact to the common reservoir of dipole-dipole interactions in order to create 15N-15N, 13C-13C, or 15N-13C cross-peaks in a 2D correlation spectrum. A thermodynamic approach can be used to understand the mechanism of magnetization mixing in various 2D correlation pulse sequences. This mechanism is suppressed under magic-angle spinning, when mixing via direct cross-polarization with protons becomes more efficient. Experimental results are presented for single-crystalline and powder samples of 15N-labeled N-acetyl-L-15N-valyl-L-15N-leucine (NAVL). In addition to the thermodynamic analysis of mixing pulse sequences, two different new mixing sequences utilizing adiabatic pulses are also experimentally demonstrated.     

Relation between signature splitting in rotational bands of odd nuclei and the amplitude of the Ω=1/2 component

The relation between signature splitting in the spectra of rotational bands of odd nuclei and the structure of wave functions of these states is investigated. Rotational bands are considered both in axisymmetric nuclei and in nuclei that do not possess axial symmetry. A simple formula is obtained that makes it possible to extract the amplitude of the Ω=1/2 wave-function component from experimental data on energy spectra.     

Angular distribution of gamma quanta in the capture of polarized μ−-mesons by atomic nuclei

The capture of a polarized ^–-meson from theK-orbit of a mesic atom is investigated for the case when the nucleus after ^–-capture is in an excited state and emits a -quantum of multipolarityL (any type). The angular distribution of circular polarized -quanta with respect to the direction of the polarization of the ^–-meson on theK-orbit is obtained for the case of allowed transitions (according to the Morita-Fujii classification).

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- ^–-

^–- K- ^–- - L ( ). - ^–- K- ( -).

     

Radiative capture of π−-mesons by light nuclei in a current algebra model

The probabilities of capture of ^–-mesons by nuclei³He,⁶Li,⁶C, and¹⁴N from 1s- and 2p-shells of mesic atoms are calculated by a hard-pion current algebra.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 45–50, November, 1986.     

K − absorption in nuclei by two and three nucleons

It will be shown that the peaks in the (Λp) and (Λd) invariant mass distributions, observed in recent FINUDA experiments and claimed to be signals of deeply bound kaonic states, are naturally explained in terms of K ^? absorption by two or three nucleons leaving the rest of the original nuclei as spectator. For reactions on heavy nuclei, the subsequent interactions of the particles produced in the primary absorption process with the residual nucleus play an important role. Our analyses leads to the conclusion that at present there is no experimental evidence of deeply bound K ^? state in nuclei. Although the FINUDA experiments have been done for reasons which are not supported a posteriori, some new physics can be extracted from the data.     

Study of the preequilibrium mechanism for individual channels of the 159Tb, 209Bi(α, charged particle xnγ) reactions with particle-γ coincidences

The mechanism of preequilibrium emission of protons, deuterons and tritons has been studied for α-induced reactions on ¹⁵⁹Tb and ²⁰⁹Bi using particle-γ coincidence techniques. The experiments were carried out for α energies of 45, 75 and 110 MeV and the charged ejectiles were detected at angles of 45°, 90° and 135° with respect to the beam direction. The experimental technique allowed to identify individual reaction channels and to determine their differential cross sections as a function of the ejectile energy. The most important finding is that the cross sections of the individual reaction channels show pronounced peaks and additionally low-energy tails for higher beam energies. The peaks are related to the emission of a charged particle in the preequilibrium phase followed by neutron evaporation indicating a breakup-fusion mechanism. For the tails at least two fast particles are emitted resulting from a breakup-fusion mechanism with three or more particles in the continuum. The data furthermore contain information about the depopulation mechanism and it was found that the entry point for compound nucleus decay moves away from the yrast line with increasing beam energy.