The structure of 74Se at low energy was investigated via spectroscopy of internal conversion electrons at the INFN Legnaro National Laboratories (LNL). A set of internal K-conversion coefficients and ...monopole transition strengths was measured. A large ρ2(E0;22+→21+)⋅103=210(130) value was deduced. This result, in addition to a low upper limit for the 03+→02+ electron transition, casts in doubt a simple interpretation of the 74Se low-lying structure, in particular the recently proposed spherical, vibrational character. New microscopic beyond-mean-field calculations generally agree with the experimental results and are capable of producing a large ρ2(E0;22+→21+) value, even if still a factor ≈7 smaller than the experiment. Triaxiality and a complex shape-coexistence and mixing scenario seem responsible for this unexpected experimental result.
There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, ...which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we observed the low-lying quantum states in
Rn and
Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.
Coulomb excitation of Zn74,76 Illana, A.; Zielińska, M.; Huyse, M. ...
Physical review. C,
10/2023, Letnik:
108, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The first experiment using radioactive beams post-accelerated by the HIE-ISOLDE facility has enabled to obtain a precise set of B(E2)transition probabilities in neutron-rich Zn74,76 isotopes. The ...resulting B(E2; 2+1→0+1) values are consistent with those determined in earlier REX-ISOLDE measurements. While the B(E2; 4+1→2+1) transition probability in Zn76 is also in agreement with earlier Coulomb-excitation results, the value obtained for Zn74 is considerably lower. For the first time, a spectroscopic quadrupole moment of the 2+1 state was measured for an exotic nucleus in this mass region. A detailed comparison is presented with large-scale shell-model and Monte Carlo shell-model calculations.
Coulomb excitation of Rn 222 Spagnoletti, P.; Butler, P. A.; Gaffney, L. P. ...
Physical review. C,
02/2022, Letnik:
105, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb ...excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3− and 2+→5− transitions were found to be respectively 2360+300−210efm3 and 2300+300−500efm3 while a smaller value, 1200+500−900efm3, was found for the 2+→1− transition. In addition, four excited non-yrast states were identified in this work via γ−γ coincidences.
The collective structure of 106Cd is elucidated by multi-step Coulomb excitation of a 3.849 MeV/A beam of 106Cd on a 1.1 mg/cm2208Pb target using GRETINA-CHICO2 at ATLAS. Fourteen E2 matrix elements ...were obtained. The nucleus 106Cd is a prime example of emergent collectivity that possesses a simple structure: it is free of complexity caused by shape coexistence and has a small, but collectively active number of valence nucleons. This work follows in a long and currently active quest to answer the fundamental question of the origin of nuclear collectivity and deformation, notably in the cadmium isotopes. The results are discussed in terms of phenomenological models, the shell model, and Kumar-Cline sums of E2 matrix elements. The 〈02+||E2||21+〉 matrix element is determined for the first time, providing a total, converged measure of the electric quadrupole strength, 〈Q2〉, of the first-excited 21+ level relative to the 01+ ground state, which does not show an increase as expected of harmonic and anharmonic vibrations. Strong evidence for triaxial shapes in weakly collective nuclei is indicated; collective vibrations are excluded. This is contrary to the only other cadmium result of this kind in 114Cd by C. Fahlander et al. (1988) 38, which is complicated by low-lying shape coexistence near midshell.
There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity ...in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.
Low-energy Coulomb excitation is one of the simplest and most known tools to study the nuclear shape; for this reason it is nowadays widely used at radioactive beam facilities. The Selective ...Production of Exotic Species (SPES) facility, for the acceleration of radioactive beams will soon provide the first exotic beams at the Laboratori Nazionali di Legnaro (LNL) in Italy. To this end a new particle detector (Silicon PIe DEtectoR) to be used for Coulomb excitation studies has been installed at LNL. SPIDER has been coupled to the GALILEO array of germanium detectors, and a number of experiments have been already successfully performed. This paves the way for future experiments with the radioactive beams provided by the SPES facility.
Fourier Transform Raman Spectroscopy was used to investigate the molecular changes of structural proteins in human skin subjected to strain. In the Raman spectrum of unstrained skin, bands assigned ...mainly to collagen and elastin were observed at 1658cm−1 (amide I), 1271 and 1255cm−1 (amide III), and 935 and 817cm−1 (CC stretching modes of the protein backbone). Moreover, bands characteristic for amino acids were observed at 1336cm−1 (desmosine), 1004cm−1 (phenylalanine), 919 and 856cm−1 (proline), and 877cm−1 (hydroxyproline). Positions and intensities of the listed Raman bands were analysed as a function of applied strain. A clear correlation between Raman wavenumbers and the level of mechanical stress was established. Wavenumbers of the analysed bands changed gradually with increasing strain. Distinct responses, depending on the sample cutting direction, i.e. longitudinal or perpendicular to the Langer’s lines, were noticed. It was concluded that elastin and non-helical domains of collagen are initially involved in the load transfer and triple helices of collagen are gradually joining this process. It was proved that Raman spectroscopy give insight into skin deformation micromechanics.
Direction-depending mechanical properties of human thigh skin were measured. Raman spectroscopy was used to investigate the molecular changes of structural proteins in a human skin subjected to a uniaxial strain. It has been found that collagen and elastin fibres are responsible for skin strength and molecular mechanism for load transferring has been proposed. Display omitted
► Mechanical properties of human thigh skin were investigated. ► Uniaxial tensile tests were performed depending on skin cutting direction. ► Raman scattering studies revealed structural changes under stress. ► A molecular mechanism for load transferring by proteins was proposed.
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