Spectroscopic nuclear quadrupole moments

A ‘year-2001’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-1992’ set, a major revision of the value or a considerable improvement of the accuracy is reported for ⁶ ₃Li, ₇N, ¹⁹ ₉F (197 keV, I = 5/2), ₁₁Na, ₁₃Al, ₂₁Sc, ₂₂Ti, ₂₆Fe (14 keV, I = 3/2 Mössbauer state), ₃₁Ga, ₃₂Ge, ⁷⁷ ₃₄Se (250 keV, I = 5/2 state), ₃₅Br, ₃₆Kr, ₃₇Rb, ₃₉Y, ₄₀Zr, ¹⁰⁰ ₄₅Rh, ₅₀Sn (24 keV, I = Mössbauer state), ₅₃I, ₅₄Xe, ₅₅Cs and ₈₃Bi.     

In-beam measurements of nuclear moments

Nuclear moments contribute valuable information to nuclear structure studies of nuclei under extreme conditions, such as nuclei at high angular momentum or far from stability. While the magnetic moment is sensitive to the nature of the participating nucleons (neutron or proton) the quadrupole moment is a direct measure for nuclear deformation.     

Identification of band structures in the 137La nucleus

High-spin states of ¹³⁷La have been investigated with the reaction ¹³⁰Te(¹¹B, 4n) at a beam energy of 50MeV. The level scheme of ¹³⁷La has been expanded with spin up to 33/2ℏ. Several new bands have been found in this nucleus. A band crossing in the band based on the 17/2^- level has been observed at a rotational frequency of ℏω ∼ 0.48MeV. From systematic comparison, this band crossing probably originates from the alignment of protons. One of the bands with strong M1 transitions is proposed as a collective oblate band ( γ ∼ -60^°).     

Description of the nuclear surface by moments

The parameters proposed by W. D. Myers to describe the radial shape dependence of the nuclear surface are shown to be as useful as they are natural. For spherical nuclei, the central radiusC, the charge radiusR, the quadratic radiusQ are redefined, and it is shown how they are interrelated by Myers' surface widthb, flair γ₃, crookedness γ₄, and the higher shape parameter γ₅. All these quantities are calculated for some special charge distribution functions. (For symmetric distributions, possessing a symmetry center atC, the odd surface momentsb ³γ₃ andb ⁵γ₅ vanish.) The connection of the surface moments Г_μ =b ^μ γ _μ with the volume momentsF _k that have been extracted by K. W. Ford and J. G. Wills from muonic atoms, is indicated.     

The determination of nuclear moments from the angular distribution of radiation emitted by dynamically polarized nuclei

A method is suggested which allows the establishment both of the sign and magnitude of quadrupole interaction and the magnitude of magnetic moment of radioactive nuclei. The dynamic polarization of these nuclei is assumed (by means of the effet solide or the method of Jeffries) as well as the subsequent change of the degree of orientation (by means of saturation of some suitable nuclear transitions). The comparison of resonant frequencies for negative and positive initial polarization gives the values of the above-mentioned quantities. The angular distribution of the intensity of radiation emitted is used for the detection of changes in the degree of polarization.     

Description of nuclear moments and nuclear spectra in the particle-rotor model

The particle-rotor model using strong coupling basis functions is briefly reviewed. Recent developments are discussed. For example, a formalism for odd-odd nuclei (and negative parity states in even nuclei) is presented. With a standard neutron-proton interaction, measured spins and moments of transitional and deformed Ho nuclei are used to extract their main configurations. Total energy calculations in the (ε, ψ)-plane based on the particle-rotor model are presented for¹⁸⁵Au.     

Nuclear moments and nuclear structure

Research activities of the Osaka Sugimoto group in the past 30 years are summarized. Developments of the perturbed angular correlation method and the new NMR method under the leadership of Sugimoto opened a wide variety of possibilities, not only in the nuclear structure study but also in studies of nuclear reactions, weak interactions and hyperfine interactions.     

Year-2017 nuclear quadrupole moments

A ‘year-2017’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-2008’ set, a major revision of the value, or an improvement of the accuracy is reported for ²₁H, ^{37, 39}₁₈Ar, ^{39, 40, 41}₁₉K, ⁶⁷₃₀Zn, ₄₈Cd, ₄₉In, ₅₀Sn (Mössbauer state), ₅₁Sb, ₈₇Fr and ₉₀Th. Slight improvements or valuable reconfirmations exist for ₄Be, ₆C, ₁₆S, ₁₇Cl, ₃₃As, ₃₅Br, ₅₃I, ₅₄Xe, ₅₆Ba, ₅₇La and ₇₂Hf.     

Simple relations for nuclear moments

Various relations for nuclearg-factors are extended, applied and discussed in view of recent experimental data. It is shown that the additivity relation can be used such that most of the corrections to theg-factor are accounted for. The isoscalar and isovector parts of theg-factor are studied in the mass regionA≦55 under the assumption of purej ⁿ configurations. For the isoscalar part the discrepancies with experiment are compatible with those for large shell-model calculations. Good results are obtained for the isovector part of theg-factor of ground states in mirror nuclei if both Gamow-Teller matrix elements, extracted from experimentalft values with an effective coupling constant ratio for Fermi and Gamow-Teller transitions, and assumptions on the seniority of the wave functions are used.     

The argon nuclear quadrupole moments

New standard values -116(2) mb and 76(3) mb are suggested for the nuclear quadrupole moments (Q) of the ³⁹Ar and ³⁷Ar nuclei, respectively. The Q values were obtained by combining optical measurements of the quadrupole coupling constant (B or eqQ/h) of the 3s²3p⁵4s[3/2]₂ (³P^o) and 3s²3p⁵4p[5/2]₃ (³D^e) states of argon with large scale numerical complete active space self-consistent field and restricted active space self-consistent field calculations of the electric field gradient at the nucleus (q) using the LUCAS code, which is a finite-element based multiconfiguration Hartree–Fock program for atomic structure calculations.     

On the P- and T-nonconserving nuclear moments

The contribution of virtual excitations of paired nucleons to T-nonconserving nuclear moments caused by T-odd nuclear forces is shown to be comparable to the contribution of the external nucleon. Taking into account the contribution of paired nucleons in the ¹²⁹Xe nucleus allows one to extract from atomic experiments the best limit on the P- and T-nonconserving nucleon-nucleon interactions. This limit approaches, by its implications, the limit on the neutron dipole moment. In the case of the P-nonconserving, but T-invariant, anapole nuclear moment the external nucleon's excitations dominate.     

Determination of the242m Am nuclear moments

The hyperfine structure of Am atoms was investigated in an atomic beam by laser spectroscopy. The observed splittings were evaluated with respect to the magnetic dipole and electric quadrupole moments of^242m Am. The results are: μ _I (^242m Am)=+0.97(5)nm,Q(^242m Am)=+6.5(2.0)b.     

Effective hamiltonian of the nuclear moments electronic shielding

An information is given allowing to use the second quantization and the effective operator methods in the ligand field theory. The operator was constructed accounting for the interaction of the multi-shell electronic configurations through a one-particle perturbation V≪R. The expression obtained is believed to be useful in microscopic calculations and phenomenological interpretation of spectroscopic experiments. As an illustration, the effective hamiltonian of the nuclear moments electronic shielding has been deduced. It was found, in particular, that the dipolar part of the hyperfine interaction contributes to the shift of the nuclear g-factor in the systems with the electronic spin S>0.     

Isoscalar currents and nuclear magnetic moments

We investigate meson-exchange current effects on isoscalar nuclear magnetic moments taking a one-boson exchange model. For some cases we find appreciable contributions, though the results are very model dependent. We also discuss the connection between exchange currents and the calculation of magnetic moments in the relativistic σ-ω model.     

Studies of nuclear second moments for pre-equilibrium nuclear reaction theories

The nuclear second moments, important inputs to pre-equilibrium reaction theories, are evaluated by assuming a simple model. The positive definite nature of the second moments is examined, and the nuclear level densities are calculated using positive definite second moments.