Electric quadrupole moments of neutron-rich nuclei 32Al and 31Al

The electric quadrupole moments for the ground states of ³²Al and ³¹Al have been measured by the β ray-detected nuclear quadrupole resonance method. Spin-polarized ³²Al and ³¹Al nuclei were obtained from the fragmentation of ⁴⁰Ar projectiles at E/A?=?95 MeV/nucleon, and were implanted in a single crystal α-Al₂O₃ stopper. The measured Q moment of ³²Al, |Q(³²Al)|?=?24(2) mb, is in good agreement with a conventional shell-model calculation with a full sd model space and empirical effective charges, while that of ³¹Al is considerably smaller than the sd calculations.     

The quadrupole moment of176Lu

The intrinsic quadrupole moment of¹⁷⁶Lu has been determined by Coulomb excitation with α-particles to be 6.98±0.10 b. Evidence for a new level at approximately 578 keV with presumably collective structure is presented.     

Electric dipole transitions in neutron-rich nuclei

The structure of neutron-rich nuclei in several isotopes is investigated by shell model calculations. We study the electric dipole (E1) transitions in C isotopes focusing on the interplay between the low-energy Pigmy strength and the giant dipole resonance (GDR). Reasonable agreement is obtained with available experimental data for the photoreaction cross sections in ¹²C, ¹³C, and ¹⁴C with the inclusion of the quenching effects. A low-energy peak in the dipole strength in ¹⁵C is associated with a single-particle motion of the 1s_1/2 valence neutron relative to the ¹⁴C core. The calculated transition strength below the GDR in C isotopes heavier than ¹⁵C is found to exhaust about 50–80% of the cluster sum rule value and 12–16% of the classical Thomas-Reiche-Kuhn sum rule value. Next, we point out that the quadrupole and magnetic moments in the odd C isotopes strongly depend on configuration, which will be useful to determine the spin parities and the deformations of the ground states of these nuclei. The electric quadrupole (E2) transitions in even C isotopes are also studied. The isotopic dependence of the E2 transition strength is found to be reasonably well explained, although the calculated strength largely overestimates the unexpectedly small strength observed in ¹⁶C. The E1 strength in ¹⁸N and ¹⁹N as well as in Ne isotopes is also investigated.     

The electric quadrupole moment of theΩ −

We estimate the electric quadrupole moment of theΩ ^? within current non-relativistic quark models. With only one-gluon exchange as a source of tensor forces we get typically a valueQ _ω=0.004 fm² which is probably very hard to measure experimentally.     

Magnetic moment and electric quadrupole moment of the anomalous186Ir ground state

The ground state nuclear moments of¹⁸⁶Ir (j ^π=5⁽⁺⁾) have been determined with NMR on oriented¹⁸⁶Ir in Ni as |μ|=3.80 _?0.02 ^+0.12 μ _n andQ=?3.00 (15)b. The quadrupole moment is consistent with an anamolousj ^π K=5⁺0 or 5⁺1 ground state configuration. The explanation of the magnetic moment in terms of pure 5⁺0 or 5⁺1 configurations would require a high collectiveg _R-factor ofg _R≧0.76. On the other hand the magnetic moment can be explained with a “normal”g _R and a mixed ground state configuration.     

The quadrupole moment of the neutron-halo nucleus11Li

The quadrupole moment ratio of⁹Li and¹¹Li was measured by a combination of in-beam laser induced nuclear polarization and Β-NMR in LiNbO₃. The result ¦Q(¹¹Li)/Q(⁹Li)¦=1.14(16) is consistent with cluster models describing¹¹Li as composed of a⁹Li core and a far extended halo of two loosely bound neutrons.     

Laser spectroscopic determination of the 50V quadrupole moment

Using the method of atomic-beam magnetic resonance, detected by laser-induced resonance fluorescence (ABMR-LIRF), the atomic ground-state hyperfine intervals of ⁵⁰V were precisely measured. A quadrupole moment ratio $\text{Q(}{}^{50}\text{V}\text{) / (}{}^{51}\text{V}\text{= ?4.03(3)}$ is obtained which results in $\text{Q(}{}^{50}\text{V}\text{) = +0.21(4)}\text{b}$.     

Exterior and interior metrics with quadrupole moment

We present the Ernst potential and the line element of an exact solution of Einstein’s vacuum field equations that contains as arbitrary parameters the total mass, the angular momentum, and the quadrupole moment of a rotating mass distribution. We show that in the limiting case of slowly rotating and slightly deformed configuration, there exists a coordinate transformation that relates the exact solution with the approximate Hartle solution. It is shown that this approximate solution can be smoothly matched with an interior perfect fluid solution with physically reasonable properties. This opens the possibility of considering the quadrupole moment as an additional physical degree of freedom that could be used to search for a realistic exact solution, representing both the interior and exterior gravitational field generated by a self-gravitating axisymmetric distribution of mass of perfect fluid in stationary rotation.     

电子的电矩

依据狄拉克方程的相关结论指出,电子除磁矩外还存在体现在高阶效应中的电矩.     

Photo-induced persistent internal quadrupole moment of a semiconductor

The persistent internal quadrupole moment which has been observed in Li-doped ZnO crystals is studied theoretically. The quadrupole moment is expressed in terms of relaxation coefficients and effective cross sections characterizing the scattering and capture processes of the photo carriers. Furthermore, it is related to the anisotropy of the mobility and of the persistent internal polarization.     

Magnetic quadrupole moment of W-boson in Kobayashi-Maskawa model

Due to CP-invariance violation a vector particle can acquire a T- and P-odd electric dipole moment and a magnetic quadrupole one. The W-boson magnetic quadrupole moment is calculated in the Kobayashi-Maskawa model. This is the only known CP-odd moment arising in this model in two-loop approximation.     

Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes

The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.     

The hyperfine quadrupole moment of muonium in the ground state

The quadrupole moment of the ground state of the μ⁺e^? atom is calculated to be (3m_em_μ)^?1; effects in a crystal are briefly discussed.     

Measurement of electric quadrupole moments of neutron-rich nuclei14B and15B

The experimental study of nuclear moments of several neutron-rich nuclei, using the phenomenon of ejectile spin polarization in the projectile fragmentation reaction, is reported. The spin-polarized fragments¹⁴B and¹⁵B were produced in the fragmentation of¹⁸O projectiles on a Nb target at 64.7 MeV/u. They were implanted into a Mg single crystal, and the quadrupole momentsQ were determined by the-NMR method. The results, ¦Q(¹⁴B)¦ =29.84 ±0.75 mb and ¦Q(¹⁵B)¦=38.01 ±1.08 mb, are compared with theoretical models. Shell model calculations in a 0 model space, using effective charges commonly accepted in this mass region, predict values about 40% larger than the experimentalQ(¹⁵B). Agreement is obtained when a much smaller effective charge for neutrons is employed. The method was also applied to the measurement of the magnetic moments of¹⁷N and¹⁷B. The result reveals an important contribution of configurations with excess neutrons coupled to formJ =2⁺.     

Sign of the quadrupole moment of proton drip-line nucleus 8B

The sign of the quadrupole coupling constant eqQ of ⁸B in ZrB₂ is determined to be positive through the β-delayed α-ray anisotropy measurement combined with the spin manipulation technique by use of the β-NMR. According to the theoretical calculation of the electric field gradient in ZrB₂, the sign of the quadrupole moment of ⁸B is deduced to be positive. This revised version was published online in August 2006 with corrections to the Cover Date.