Transition charge densities of low-lying collective states in even Zn isotopes

The inelastic electron scattering cross sections for the quadrupole transitions to the 2₁⁺ and 2₂⁺ states in the even Zn isotopes ⁶⁴Zn, ⁶⁶Zn and ⁶⁸Zn and for the hexadecapole transition to the 4⁺₁ state in ⁶⁴Zn have been measured in a momentum transfer range up to q = 2.2 fm^?1. In the frame-work of the vibrational model these states are considered as one- and two-quadrupole-phonon states. The measurements are characterized by high statistical accuracy and by an overall resolution of δE/E₀ = 10^?3 which permitted separation of almost all members of the two-phonon triplet. The measured cross sections are analyzed with phenomenological models as well as with a Fourier-Bessel expansion of the transition charge density. The latter analysis yields realistic error bands for the transition charge densities and model-independent values for the reduced transition probabilities and transition radii.     

Evolution of intrinsic nuclear structure in medium mass even-even Xenon isotopes from a microscopic perspective

In this study, the multi-quasiparticle triaxial projected shell model (TPSM) is applied to investigate \begin{document}$\gamma$\end{document}-vibrational bands in transitional nuclei of \begin{document}$^{118-128}{\rm{Xe}}$\end{document}. We report that each triaxial intrinsic state has a \begin{document}$\gamma$\end{document}-band built on it. The TPSM approach is evaluated by the comparison of TPSM results with available experimental data, which shows a satisfactory agreement. The energy ratios, B(E2) transition rates, and signature splitting of the \begin{document}$\gamma$\end{document}-vibrational band are calculated.     

Intermediate energy proton scattering and nuclear transition densities in nickel isotopes

Using the high-resolution spectrometer SPES-I, the angular distribution of 1.047 GeV protons scattered from ⁵⁸Ni, ⁶⁰Ni, ⁶²Ni, ⁶⁴Ni have been measured in the angular range 4–18°, up to 4.8 MeV excitation energy. The data are analyzed within the framework of Glauber multiple scattering theory using a spin-dependent NN scattering amplitude. The parameters of the neutron density distributions have been determined by a χ² analysis of elastic scattering. The inelastic data corresponding to the first 2⁺ and 3⁻ states are analyzed with the collective model and an attempt has been made to extract information about the corresponding neutron transition densities.     

Tests of interacting boson model wave functions from measured gyromagnetic ratios of states in the even Os isotopes

The gyromagnetic ratios of the 2₁⁺, 2₂⁺, and 4₁⁺ states in ^188,190,192Os were experimentally measured. It is shown that the hamiltonians of standard interacting boson models (IBM-1 and -2) fit to level spectra and B(E2) rates fail to account for either the intra-nucleus or mass-dependent g-factor variations of these states in these Os isotopes.     

Isotope shifts in Sm II and changes in mean-square nuclear charge radii of the stable even Sm isotopes

Isotope shifts have been measured in Sm II from which the shifts between pure configurations 4f ⁶ s and 4f ⁶5d can be determined. The specific mass shift for such a “transition” was estimated to be (?1±2)mK for a change of two neutrons. The values derived for the change in the nuclear charge distribution,δ〈r ²〉, are in good agreement with the results obtained from isotope shift measurements in Sm I (H. Brand et al.: J. Phys. B11, L99, 1978). The weighted mean values representing the best information onδ〈r ²〉 presently available are in fm²: [144, 148] 0.488(23); [148, 150] 0.285(14); [150, 152] 0.400(19); [152, 154] 0.217(11).     

The beta decay of Pm146 with microscopic nuclear wave functions

Explicit numerical values are given for the matrixelements of the first forbiddenβ ^?-decay of Pm¹⁴⁶ to the 2⁺-state of Sm¹⁴⁶. The odd-odd nucleus Pm¹⁴⁶ is assumed to have a structure similar to neighboured even-even nuclei to which an odd neutron and an odd proton are coupled. The wavefunctions of the even-even nuclei are calculated starting from Bohrs Hamiltonian.     

Hyperfine structure and nuclear magnetic moments of some neutron-deficient thallium isotopes

Using the atomic-beam magnetic resonance method, hyperfine structure (h.f.s.) measurements have been performed in the²P_1/2 electronic ground state of the neutron-deficient thallium isotopes^193–202Tl. In the doubly odd isotopes, the magnetic dipole hyperfine interaction constantsa were determined, while in the odd-A isotopes, direct measurements of the nuclearg-factors,g _I , were made. The electronicg-factor was measured in¹⁹⁸Tl. The magnetic dipole moments of the doubly odd isotopes have been evaluated by a direct comparison with known values in the stable isotope²⁰³Tl. The moments of the odd-A isotopes are in agreement with pervious measurements by optical spectroscopy. A discussion of the magnetic dipole moments in terms of different nuclear models is included. The moments of the 2^? nuclear ground states of the doubly odd isotopes may be interpreted as arising from a combination of the configurations 2^? (πs_1/2 vf_5/2) and 2^? (πs_1/2 vp_3/2).     

The hyperfine structure and nuclear moments of some neutron-deficient as isotopes

The hyperfine structure of the¹³⁹La II line 5d ^{2 3} F→5d4f ³ F ₄ ⁰ atλ=579.8 nm has been investigated by means of collinear laser spectroscopy on a fast La⁺ beam. AmongΔF=0, ±1 hyperfine transitions,gDF=±2 transitions have been observed. An interpretation of theseΔF=±2 transitions as well as their relative line strengths is given by means of a three-quantum process.     

Precise atomic mass difference determinations between some stable isotopes of Ge,As and Se

The 1 m radius, high-resolution mass spectrometer at the University of Manitoba (“Manitoba II”) has been used to determine 11 atomic mass differences between some stable isotopes of Ge, As and Se. These values are of greater accuracy and precision than existing data. Their consistency has been checked by a major least-squares adjustment involving relevant data in the region. Results include improved S_2n values for several nuclides and the energies available for the ββ decays of ⁷⁶Ge and ⁷⁴Se, respectively.     

Calculation of the Peierls-Yoccoz translational mass for Hartree-Fock wave functions

The Peierls-Yoccoz projection method for translation is applied to Hartree-Fock wave functions constructed on a mesh for ${}^4\text{He}$ and ${}^{16}\text{O}$. As expected, the mass parameters differ from the nuclear masses, indicating a breaking of galilean invariance.     

Detailed study of nuclear charge and mass densities: (I). Surface and asymptotic properties

Theoretical and experimental densities are analyzed and compared in detail, in particular in the surface region. For this purpose nuclear size parameters are discussed and new sets of surface parameters are proposed. It is shown that the densities are very close to the error function in the external part of the surface and can be characterized there by two new parameters. For very large r the densities show an exponential behaviour which is analyzed in terms of single-particle density distributions. Furthermore, the effects of the asymmetry, spin-orbit and Coulomb forces on the density distributions are discussed.     

Subshell effect in mean square charge radii of stable even cadmium isotopes

Isotope shifts of the 467.8 nm line have been measured by Doppler-free saturation spectroscopy for the even Cd isotopes 106 through 116. The differential changes in mean square charge radii derived from the field shifts show a pronounced break in their trend atN=64, giving evidence for the closure of theg _7/2 neutron subshell. The average charge radii determined from our data and the rms radius of¹¹⁴Cd measured with muonic X-rays verify the general trend predicted by the droplet model but are off by about 35 mfm on an absolute scale. A consistent interpretation of δ〈r ²〉 further supports the necessity for considering changes in the skin thickness of the nuclear charge distribution.     

Isotope shifts of the 557 nm transition in even krypton isotopes

Doppler free saturation spectroscopy has been applied to obtain accurate values for the isotope shifts of the 2p₃-1s₅ transition in even krypton isotopes. A field shift was found which reflects a much larger increase of the average charge distribution for the first half of the $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ neutrol shell compared to the second half.     

Evolution of nuclear charge radii in copper and indium isotopes

Systematic trends in nuclear charge radii are of great interest due to universal shell effects and odd-even staggering (OES). The modified root mean square (rms) charge radius formula, which phenomenologically accounts for the formation of neutron-proton (np) correlations, is here applied for the first time to the study of odd-Z copper and indium isotopes. Theoretical results obtained by the relativistic mean field (RMF) model with NL3, PK1 and NL3^* parameter sets are compared with experimental data. Our results show that both OES and the abrupt changes across begin{document}$ N = 50 $end{document} and 82 shell closures are clearly reproduced in nuclear charge radii. The inverted parabolic-like behaviors of rms charge radii can also be described remarkably well between two neutron magic numbers, namely begin{document}$ N = 28 $end{document} to 50 for copper isotopes and begin{document}$ N = 50 $end{document} to 82 for indium isotopes. This implies that the np-correlations play an indispensable role in quantitatively determining the fine structures of nuclear charge radii along odd-Z isotopic chains. Also, our conclusions have almost no dependence on the effective forces.     

Velocity fields and transition densities in nuclear collective modes

The shape of the deformations occurring in nuclear collective modes is investigated by means of a microscopic approach. Analytical solutions of the equations of motion are obtained by using simplified nuclear potentials. It is found that the structure of the velocity field and of the transition density of low-lying modes is considerably different from the predictions of irrotational hydrodynamic models. The low-lying octupole state is studied in particular detail by using the Skyrme force.     

Charge and transition densities of samarium isotopes in the interacting boson modei

The interacting boson approximation (IBA) model has been used to interpret the ground-state charge distributions and lowest 2⁺ transition charge densities of the even samarium isotopes for A = 144–154. Phenomenological boson transition densities associated with the nucleons comprising the s- and d-bosons of the IBA were determined via a least squares fit analysis of charge and transition densities in the Sm isotopes. The application of these boson transition densities to higher excited 0⁺ and 2⁺ states of Sm, and to 0⁺ and 2⁺ transitions in neighboring nuclei, such as Nd and Gd, is described. IBA predictions for the transition densities of the three lowest 2⁺ levels of ¹⁵⁴Gd are given and compared to theoretical transition densities based on Hartree-Fock calculations. The deduced quadrupole boson transition densities are in fair agreement with densities derived previously from ¹⁵⁰Nd data. It is also shown how certain moments of the best fit boson transition densities can simply and successfully describe rms radii, isomer shifts, B(E2) strengths, and transition radii for the Sm isotopes.     

IBA-2 model calculation on even mass tellurium isotopes compared with results of recent nuclear orientation experiments

Calculations using the IBA-2 model code are presented for even-even tellurium isotopes¹¹⁸Te to¹²⁴Te. Three parameter sets are used, two from previous work and a third chosen to give optimum fit to experimental positive parity energy levels and B(E2) ratios. With only two additional parameters, each with simple physical interpretation, the three parameter sets are shown to give excellent fits to the known collective negative parity states in these isotopes. Failure to fit the O ₂ ⁺ ,O ₃ ⁺ and 2 ₃ ⁺ levels suggests these may be 4p-2h intruder states, although their Behaviour with varying neutron number is not as clearly characteristic of such configurations as is found for the 2p-4h states in Cd isotopes.     

Empirical transverse charge densities in the nucleon and the nucleon-to-delta transition

Using only the current empirical information on the nucleon electromagnetic form factors we map out the transverse charge density in proton and neutron as viewed from a light front moving towards a transversely polarized nucleon. These charge densities are characterized by a dipole pattern, in addition to the monopole field corresponding with the unpolarized density. Furthermore, we use the latest empirical information on the N-->Delta transition form factors to map out the transition charge density which induces the N-->Delta excitation. This transition charge density in a transversely polarized N and Delta contains both monopole, dipole and quadrupole patterns, the latter corresponding with a deformation of the N and Delta charge distribution.     

Odd-even staggering in nuclear charge radii of neutron-rich europium isotopes

Nuclear magnetic dipole and electric quadrupole moments and changes in mean square charge radii for the neutron-rich^155–159Eu isotopes have been measured using resonance ionization spectroscopy at the IRIS facility. It has been found that the isotopes withN>92, unlike the isotopes with 89≦N≦92, have an ordinary character of odd-even staggering in nuclear charge radii. This means that the octupole deformation attributed previously to the europium nuclei around¹⁵⁴Eu does not display itself in the charge radii of heavier europium isotopes.