J. Timár

Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin–orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron–proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron–proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

The first candidate for chiral nuclei in the A~80 mass region: 80Br

Abstract Excited states of 80Br have been investigated via the 76Ge(11B, α 3 n ) and 76Ge(7Li, 3n) reactions and a new Δ I = 1 band has been identified which resides ∼ 400 keV above the yrast band. Based on the experimental results and their comparison with the triaxial particle rotor model calculated ones, a chiral character of the two bands within the π g 9 / 2 ⊗ ν g 9 / 2 configuration is proposed, which provides the first evidence for chirality in the A ∼ 80 region.

Radiosensitivity of human prostate cancer cells can be modulated by inhibition of 12-lipoxygenase.

Nearly 30% of prostate cancer (PCa) patients treated with potentially curative doses relapse at the sites of irradiation. How some tumor cells acquire radioresistance is poorly understood. The platelet-type 12-lipoxygenases (12-LOX)-mediated arachidonic acid metabolism is important in PCa progression. Here we show that 12-LOX confers radioresistance upon PCa cells. Treatment with 12-LOX inhibitors baicalein or BMD122 sensitizes PCa cells to radiation, without radiosensitizing normal cells. 12-LOX inhibitors and radiation, when combined, have super additive or synergistic inhibitory effects on the colony formation of both androgen-dependent LNCaP and androgen-independent PC-3 PCa cells. In vivo, the combination therapy significantly reduced tumor growth.

Structure of 66Ga from (p, nγ) reaction

Abstract γ-ray, γγ-coincidence, and internal conversion electron spectra were measured with Ge(HP), as well as superconducting and traditional magnetic lens plus Si(Li) electron spectrometers at different bombarding proton energies between 6.5 and 7.1 MeV. Energies and relative intensities of 131 (among them 52 new) 66Ga γ-rays have been determined. Internal conversion coefficients of 33 transitions were measured for the first time. A more complete level scheme with new levels, γ-ray branching ratios, level spin and parity values has been deduced. The energy spectrum and electromagnetic properties were calculated on the basis of an interacting boson-fermion-fermion/truncated quadrupole phonon model for odd-odd nuclei. The model calculations reasonably describe the level spectra and electromagnetic properties of 64Zn, 65Ga, 65Zn and 66Ga nuclei with consistent parametrization.

Evidence for multiple band terminations in 102Pd

Abstract The level structure of 102 Pd has been investigated using data collected with the Eurogam 2 array. Several cascades of γ-rays have been established up to high spins. Termination of rotational bands has been observed at I π = 28 − and 32 + , and tentatively at I π = 38 + and 42 + . The nucleus 102 Pd is the first case where rotational bands built on valence space configurations are followed from spin close to zero up to termination and, at higher spins, a smooth rotational band which appears to terminate is built on core excited configurations.

High-spin study of 128Ce and systematics of quasiparticle pair alignment

Abstract High-spin states have been studied in 128 Ce, produced in the 100 Mo( 32 S,4n) reaction, using the Euroball γ -ray spectrometer. A quadruples analysis ( γ 4 ) of the data has extended several bands to high spin. Systematics of quasiparticle alignments in cerium isotopes and relevant isotonic chains are discussed and compared to Woods–Saxon cranking calculations.

Structure of the 68Ga nucleus from (α, nγ) reaction

Abstract Single-γ, γγ-coincidence and internal-conversion electron spectra of the 65 Cu(α, nγ) 68 Ga reaction were measured with Ge(HP) γ-ray and superconducting magnetic lens plus Si(Li) electron spectrometers at 14.5 MeV α-particle energy. The energies and relative intensities of 98 γ-transitions have been measured. Internal-conversion coefficients were determined for 19 transitions. A more complete level scheme with many new levels, γ-ray branching ratios, level spin and parity values have been deduced. The energy spectrum and electromagnetic moments were calculated on the basis of the interacting boson-fermion-fermion/truncated quadrupole phonon model for odd-odd nuclei (IBFFM/OTQM).

Nuclear structure of 108In

Abstract γ-ray and γγ-coincidence spectra of the 108 Cd ( p, n γ) 108 In reaction were measured with Ge(Li), Ge(HP, LEPS), and Ge(HP) spectrometers for different bombarding proton energies between 6.8 and 9.0 MeV, The energies and relative intensities of 142 108 In transitions (including 131 new ones) have been determined. The electron spectrum of the reaction was measured with a superconducting magnetic lens plus Si(Li) detector and independently with combined intermediate-image magnetic plus Si(Li) spectrometers at E p = 7.2 MeV. Internal conversion coefficients of 19 transitions in 108 In have been determined. The angular distributions of γ-rays were measured at 6.8 and 7.2 MeV bombarding proton energies. A more complete level scheme of 108 In has been deduced which contains 54 levels below 1630 keV excitation energy. On the basis of the internal conversion coefficients of transitions, Hauser-Feshbach analysis of(p, n) reaction cross sections, γ-ray angular distributions and other arguments, spin and parity assignments were made to 24 excited 108 In levels. Lifetime measurements were performed by a delayed coincidence method. The energies of several 108 In proton-neutron multiplets were calculated on the basis of the parabolic rule derived from the cluster-vibration model. Interacting boson-fermion-fermion/odd-odd truncated quadrupole phonon model calculations were also performed. The calculations gave a reasonable description of the energy-level spectrum and electromagnetic properties of 108 In.

Neutron-skin thickness from the study of the anti-analog giant dipole resonance

The γ-decay of the anti-analog of the giant dipole resonance (AGDR) to the isobaric analog state has been measured following the p( 124Sn,n) reaction at a beam energy of 600 MeV/nucleon. The energy of the transition was also calculated with state-of-the-art self-consistent relativistic random-phase approximation (RPA) and turned out to be very sensitive to the neutronskin thickness (ΔRpn). By comparing the theoretical results with the measured one, the ΔRpn value for 124Sn was deduced to be 0.21 ± 0.07 fm, which agrees well with the previous results. The present method offers new possibilities for measuring the neutron-skin thicknesses of very exotic isotopes.

Lifetime measurements and dipole transition rates for superdeformed states in 190Hg

The Doppler-shift attenuation method was used to measure lifetimes of superdeformed (SD) states for both the yrast and the first excited superdeformed band of 190Hg. Intrinsic quadrupole moments Q o were extracted. For the first time, the dipole transition rates have been extracted for the inter-band transitions which connect the excited SD band to the yrast states in the second minimum. The results support the interpretation of the excited SD band as a rotational band built on an octupole vibration.