Search

The hyperfine coupling constants of the proton dripline odd-odd $^{40}$Sc nucleus were deduced from the hyperfine spectrum of the $3d4s\,^3\text{D}_2$\,$\leftrightarrow$\,$3d4p\,^3\text{F}^\circ_3$ transition in Sc II, measured by the bunched beam collinear laser spectroscopy technique. The ground state magnetic dipole and electric quadrupole moments were determined for the first time as $\mu$\,=\,$+5.57(4)(2)\,\mu_N$ and $Q$\,=\,$+42(38)(28)\,e^2\;{\rm fm^2}$, respectively. The magnetic moment is well reproduced by the additivity rule with magnetic moments of neighboring odd-even nuclei in the vicinity of the doubly-magic $^{40}$Ca nucleus. An ab-initio multishell valence-space Hamiltonian was also employed to calculate the magnetic moment of $^{40}$Sc, which spans across the $sd$ and $fp$ nuclear shells, where we obtained good agreements.

A laser wavelength meter was calibrated to ±1 MHz 1 $$\sigma$$ using transitions in molecular iodine at around 700 nm, where precise experimental measurements of iodine lines are sparse. Two saturation absorption spectroscopy systems were used to measure and characterize the R(118)(2-8) a10, R(54)(3-9) a1 , and P(48)(3-9) a15 hyperfine lines of molecular iodine near 700 nm. The transition frequencies were measured using a frequency comb and used to calibrate the wavelength meter. Additionally, the full hyperfine spectrum of the R(54)(3-9) transition was obtained and fitted using a theoretical model allowing for hyperfine coupling constants to be deduced, which agreed with theoretical values.

The nuclear root-mean-square charge radius of ^{54}Ni was determined with collinear laser spectroscopy to be R(^{54}Ni)=3.737(3) fm. In conjunction with the known radius of the mirror nucleus ^{54}Fe, the difference of the charge radii was extracted as ΔR_{ch}=0.049(4) fm. Based on the correlation between ΔR_{ch} and the slope of the symmetry energy at nuclear saturation density (L), we deduced 21≤L≤88 MeV. The present result is consistent with the L from the binary neutron star merger GW170817, favoring a soft neutron matter EOS, and barely consistent with the PREX-2 result within 1σ error bands. Our result indicates the neutron-skin thickness of ^{48}Ca as 0.15-0.21 fm.

One of the most important global properties of the atomic nucleus is its size. Experimentally determined nuclear charge radii carry unique information on the nuclear force and complex dynamics of protons and neutrons moving inside the nucleus. The intricate behaviour of charge radii along the chain of Ca isotopes, including the unexpectedly large charge radius of neutron-rich 52Ca, poses a daunting challenge for nuclear theory1. Here we present the measurements of the charge radii of proton-rich isotopes 36,37,38Ca, whose properties are impacted by the interplay between nuclear superfluidity and weak binding. Calculations carried out within nuclear density functional theory show that the combination of a novel interaction2 and a state-of-the-art theoretical method can successfully explain the behaviour of charge radii from the lightest to the heaviest Ca isotopes. Through this model, we show how the new data on 36,37,38Ca elucidate the nature of nucleonic pairing in weakly bound proton-rich isotopes. Spectral study on 36,37,38Ca isotopes and calculations based on density functional theory reveal the interplay between charge radii and nucleonic pairing correlations.

The isotope shifts of the $3{d}^{9}4s^{3}D_{3}\ensuremath{\rightarrow}3{d}^{9}4p^{3}P_{2}$ transition in the stable even-even nickel isotopes were measured. An improved accuracy was achieved by transforming the systematic contribution of the wavelength-meter-based laser-frequency measurement into a statistical-acting contribution by measuring the same observables at different frequency sets. A detailed King-fit analysis was performed to extract the mass-shift and field-shift parameters, which are crucial for the determination of the charge radii of short-lived isotopes from recently measured isotope shifts. A critical dependence of the achievable charge-radius accuracy on the choice of the reference isotope in the King-fit analysis was observed and is discussed.

An approach to determine the kinetic beam energy at the ${10}^{\ensuremath{-}5}$ level is presented, which corresponds to an improvement by more than one order of magnitude compared with conventional methods. Particularly, collinear fluorescence and resonance-ionization spectroscopy measurements on rare-isotope beams, where the beam energy is a major contribution to the uncertainty, can benefit from this method. The approach is based on collinear spectroscopy and requires no special equipment besides a wavelength meter, which is commonly available. Its advent is demonstrated in a proof-of-principle experiment on a Ni beam. In preparation for the energy measurement, the rest-frame transition frequencies of the $3{d}^{\phantom{\rule{0.16em}{0ex}}9}4s{\phantom{\rule{0.16em}{0ex}}}^{3}{D}_{3}\ensuremath{\rightarrow}3{d}^{\phantom{\rule{0.16em}{0ex}}9}4p{\phantom{\rule{0.16em}{0ex}}}^{3}{P}_{2}$ transitions in neutral nickel isotopes have been identified to be ${\ensuremath{\nu}}_{0}{(}^{58}\mathrm{Ni})=850\phantom{\rule{0.16em}{0ex}}343\phantom{\rule{0.16em}{0ex}}678\phantom{\rule{0.16em}{0ex}}(20)$ MHz and ${\ensuremath{\nu}}_{0}{(}^{60}\mathrm{Ni})=850\phantom{\rule{0.16em}{0ex}}344\phantom{\rule{0.16em}{0ex}}183\phantom{\rule{0.16em}{0ex}}(20)$ MHz.

The authors explore correlations between the charge radii of mirror nuclei and the structure of neutron stars

A radiofrequency quadrupole (RFQ) ion beam cooler and buncher has been developed to deliver bunched beams with low transverse emittance, energy spread, and time spread to the BECOLA collinear laser spectroscopy system at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The beam cooler and buncher contains new features which enhance performance, especially for high count rate beams, as well as simplifying construction, maintenance, and operation. The transverse emittance, energy spread, and time spread of the bunched beam, as well as buncher efficiency are reported, showcasing the capabilities of the BECOLA facility to perform collinear laser spectroscopy measurements with bunched rare isotope beams at NSCL and at the future Facility for Rare Isotope Beams (FRIB).

A pulsed laser system has been installed at the BECOLA facility at NSCL/MSU to develop electronic population manipulation techniques for trapped ions of rare isotopes. A simulation has been developed to evaluate possible optical pumping schemes and estimate expected increase in the population of an energy level used in subsequent laser spectroscopy measurements. Development progress is on time and commissioning tests with stable Zr isotopes are planned.

The hyperfine coupling constants of neutron deficient $^{37}\mathrm{Ca}$ were deduced from the atomic hyperfine spectrum of the $4s\phantom{\rule{0.16em}{0ex}}^{2}S_{1/2}\phantom{\rule{0.16em}{0ex}}\ensuremath{\leftrightarrow}\phantom{\rule{0.16em}{0ex}}4p\phantom{\rule{0.16em}{0ex}}^{2}P_{3/2}$ transition in Ca ii, measured using the collinear laser spectroscopy technique. The ground-state magnetic-dipole and spectroscopic electric-quadrupole moments were determined for the first time as $\ensuremath{\mu}=+0.7453(72){\ensuremath{\mu}}_{N}$ and $Q=\ensuremath{-}15(11)\phantom{\rule{0.16em}{0ex}}{e}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{fm}}^{2}$, respectively. The experimental values agree well with nuclear shell-model calculations using the universal sd model-space Hamiltonians versions A and B (USDA/B) in the $sd$-model space with a 95% probability of the canonical nucleon configuration. It is shown that the magnetic moment of $^{39}\mathrm{Ca}$ requires a larger non-$sd$-shell component than that of $^{37}\mathrm{Ca}$ for good agreement with the shell-model calculation, indicating a more robust closed subshell structure of $^{36}\mathrm{Ca}$ at the neutron number $N=16$ than $^{40}\mathrm{Ca}$. The results are also compared to valence-space in-medium similarity renormalization group calculations based on chiral two- and three-nucleon interactions.

The half-life of the $^{20}\mathrm{F}$ ground state was measured using a radioactive beam implanted in a plastic scintillator and recording $\ensuremath{\beta}\ensuremath{\gamma}$ coincidences together with four CsI(Na) detectors. The result, ${T}_{1/2}=11.0011{(69)}_{\mathrm{stat}}{(30)}_{\mathrm{sys}}$ s, is at variance by 17 combined standard deviations with the two most precise results. The present value revives the poor consistency of results for this half-life and calls for a new measurement, with a technique having different sources of systematic effects, to clarify the discrepancy.

The population of low-energy metastable states in Ni I subsequent to charge-exchange reactions and cascade decay was studied for 29.85 keV Ni ions impinging on a sodium vapor. The charge-exchange cross sections were calculated using a semi-classic time-dependent perturbation theory and redistribution of the population via rapid spontaneous decays was simulated. Collinear laser spectroscopy experiments were performed on four emission lines in Ni I to determine populations in low-energy metastable states: 3d94s 3D3 (204.787 cm− 1), 3d94s 3D2 (879.816 cm− 1), 3d94s 3D1 (1713.087 cm− 1) and 3d94s 1D2 (3409.937 cm− 1). Fair agreement was obtained between the simulation and experimental results. The low-energy metastable states were preferentially populated after the cascade decay in contrast to weak populations in near-resonant high-energy states in Ni I.

The BEam COoler and LAser spectroscopy (BECOLA) facility at National Superconducting Cyclotron Laboratory at Michigan State University has been commissioned online to determine charge radii and electromagnetic moments of radioactive isotopes. A radioactive 37K beam was used for the commissioning tests and a 1.29 μs beam bunch-width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 105 in resonant photon detection measurements. The hyperfine structure of 37K and its isotope shift relative to the stable 39K were determined. The obtained hyperfine coupling constants A(2 S 1/2) = 120.3 ± 1.4 MHz, A(2 P 1/2) = 15.2 ± 1.1 MHz, and A(2 P 3/2) = 1.4 ± 8 MHz, and the isotope shift δ ν 39,37 = −264 ± 3 MHz are consistent with the previously determined values, where available.

Bunched-beam collinear laser spectroscopy is performed on neutron deficient $^{52,53}\mathrm{Fe}$ prepared through in-flight separation followed by a gas stopping. This novel scheme is a major step to reach nuclides far from the stability line in laser spectroscopy. Differential mean-square charge radii $\ensuremath{\delta}⟨{r}^{2}⟩$ of $^{52,53}\mathrm{Fe}$ are determined relative to stable $^{56}\mathrm{Fe}$ as $\ensuremath{\delta}⟨{r}^{2}{⟩}^{56,52}=\ensuremath{-}0.034(13)\text{ }\text{ }{\mathrm{fm}}^{2}$ and $\ensuremath{\delta}⟨{r}^{2}{⟩}^{56,53}=\ensuremath{-}0.218(13)\text{ }\text{ }{\mathrm{fm}}^{2}$, respectively, from the isotope shift of atomic hyperfine structures. The multiconfiguration Dirac-Fock method is used to calculate atomic factors to deduce $\ensuremath{\delta}⟨{r}^{2}⟩$. The values of $\ensuremath{\delta}⟨{r}^{2}⟩$ exhibit a minimum at the $N=28$ neutron shell closure. The nuclear density functional theory with Fayans and Skyrme energy density functionals is used to interpret the data. The trend of $\ensuremath{\delta}⟨{r}^{2}⟩$ along the Fe isotopic chain results from an interplay between single-particle shell structure, pairing, and polarization effects and provides important data for understanding the intricate trend in the $\ensuremath{\delta}⟨{r}^{2}⟩$ of closed-shell Ca isotopes.

Three-step resonance ionization of atomic zirconium using Ti:Sapphire lasers is investigated for the first time. We have located eight new excited states between 41,160 and 41,824 cm−1 that could serve as the intermediate state for the second-step transition. Three-step ionization paths via two of the newly observed states have been studied and numerous high-lying and autoionizing levels are observed. Eight new Rydberg series of odd-parity are identified in the photoionization spectra. The convergence limits of these Rydberg series allow us to determine the first ionization potential of Zr to be 53,507.832(35)stat(20)sys cm−1 with an order of magnitude improvement in uncertainty over the previous measurements. In addition, our measurements for one of the selected three-step paths show that the transitions can be saturated with low to moderate laser powers.

A collinear laser-spectroscopy (CLS) system in the BEam COoler and LAser spectroscopy (BECOLA) facility was constructed at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The BECOLA facility will be used to advance measurements of nuclear properties of low-energy rare isotope beams generated via in-flight reactions and subsequent beam thermalization in a buffer gas. The CLS studies at BECOLA will complement laser spectroscopy studies of charge radii and nuclear moments mostly obtained so far at Isotope SeOn Line (ISOL) facilities. Commissioning tests of the CLS system have been performed using an offline ion source to produce stable-ion beams. The tests set the ground work for experiments at the future Facility for Rare Isotope Beams (FRIB) as well as experiments at the current Coupled Cyclotron Facility at NSCL.

We report our studies in various fields of Physics through nuclear moments utilizing the β-NMR technique, including material sciences, nuclear structures and fundamental symmetries. Especially, we focus on the recent progress in the studies on the electronic structure in Pt through Knight shifts of various impurities, lattice locations of impurities, electric field gradients, the analysis of nuclear spin in terms of its components, anomaly in the spin expectation value for 9C-9Li mirror pair, the G-parity conservation law, and the Ramsey resonance on UCN for future neutron EDM measurements.

Sensitive searches for exotic scalar and tensor couplings in nuclear and neutron decays involve precision measurements of the shape of the β-energy spectrum. We have performed a high statistics measurement of the β-energy spectrum in the allowed Gamow-Teller decay of 6He with the aim to first find evidence of the contribution due to the weak magnetism form factor. We review here the motivation, describe the principle of the measurement, summarize the theoretical corrections to the allowed phase space, and anticipate the expected statistical precision.

The performance characteristics of two charge-exchange cells (CECs) with horizontal and vertical cell configurations were determined by neutralizing a 10-keV rubidium ion beam in a potassium vapor. The neutralization efficiency and the fluorescence line shape of the 5s 2 S 1 / 2 ↔ 5 p 2P3/2 (D2) transition in neutral 85Rb were investigated as a function of the reservoir temperature used to control the potassium vapor density. The CECs exhibited similar neutralization performance and at neutralization efficiencies greater than 25–50% an asymmetric line shape of the rubidium D2 fluorescent signal was observed. The asymmetry was attributed to inelastic channels in the charge-exchange process. The rubidium D2 fluorescence line shape was fitted with a multiple Voigt function, which quantitatively models the inelastic channels. In the present Rb+ + K charge-exchange process, the optimum neutralization efficiency to accurately determine the centroid of the Rb D2 resonance line shape was obtained by fitting single Voigt functions to the resonance spectra obtained at neutralization efficiencies where inelastic processes were negligible.

A compact β -ray detecting nuclear magnetic/quadrupole resonance system with a permanent magnet was developed at ISAC/TRIUMF to measure ground-state electromagnetic moments of short-lived nuclei. Polarized Na beams produced using the collinear optical-pumping technique were used to demonstrate the properties of the system. The degree of nuclear polarization and the spin–lattice relaxation times of the 20,21,26,27,28Na isotopes in NaF, TiO2, LiNbO3, MgF2, ZnO, Pt, and Mg single crystals at room temperature are reported. The electric-quadrupole coupling constants of 20,21Na in TiO2, ZnO and Mg, and that of 27Na in ZnO are also reported. The quadrupole moments of 20,21Na were extracted from the electric-quadrupole coupling constants in ZnO, using the known quadrupole moment of 27Na.

We report recent situation of anomaly in spin expectation value found in 9 C- 9 Li mirror pair, recent analysis of the nuclear spin in terms of orbital or intrinsic and proton or neutron, and a result from the study of the G -parity conservation law through β -ray angular correlation in terms of its nuclear orientation.

A beta-ray detecting nuclear quadrupole resonance system has been developed at NSCL/MSU to measure ground-state electric quadrupole moments of short-lived nuclei produced as fast rare isotope beams. This system enables quick and sequential application of multiple transition frequencies over a wide range. Fast switching between variable capacitors in resonance circuits ensures sufficient power delivery to the coil in the beta-ray detecting nuclear magnetic resonance technique. The fast switching technique enhances detection efficiency of resonance signals and is especially useful when the polarization and/or production rate of the nucleus of interest are small and when the nuclear spin is large.

The alignment correlation terms in the β-ray angular distributions from purely spin aligned 8Li and 8B have been measured to search for the G-parity violating induced tensor term g II in the weak nucleon currents. The g II was extracted from the present alignment correlation terms, combined with the known β – α angular correlation terms and weak magnetism. This analysis permits an experimental determination of all the matrix elements necessary to extract g II . As a result, the induced tensor term was extracted as g II / g A = − 0.28 ± 0.28 (stat.) ± 0.15 (syst.) at a 1σ (68%) level. The present data and the data in the mass A = 12 and 20 systems were analyzed under the KDR model in which medium effects including the off-shell effect and meson exchange current were taken into account. We determined the 1-body contribution to be ζ = − ( 0.13 ± 0.13 ) × 10 −3 MeV −1 and the 2-body contribution to be λ = + ( 0.27 ± 0.97 ) × 10 −3 at a 1σ level.

We measured the polarization of the β-emitting 23Ne (I π =5/2+, T 1/2=37.24 s) and 25Al(I π =5/2+, T 1/2=7.18 s) produced through the one nucleon pickup reactions and 24mAl(I π =1+, T 1/2=131 ms, E ex=426keV) and 28P(I π =3+, T 1/2=270 ms) produced through charge-exchange reactions in the intermediate energy heavy ion collisions. We compared them with those from the projectile fragmentation process. The larger polarization seems to persistently be positive throughout the momentum distribution, and sharper momentum distributions suggest that nuclear friction mechanism is responsible for the polarization phenomena.

The alignment correlation term in the β-ray angular distribution from purely nuclear spin aligned 20F has been measured to test the G-parity conservation law which is one of the fundamental symmetries in the weak nucleon current. We utilized the hyperfine interaction of 20F in an MgF2 single crystal and successfully created the pure alignment from the polarization by means of the spin manipulation technique based on the β-NMR method.

The feasibility of in-beam polarization of nuclear spin in F+ beams was studied. It was demonstrated that metastable atomic fluorine could be optically pumped on the closed transition (3s 4P5/2-3p 4D7/2) at 686 nm. The metastable production efficiency in sodium vapor was measured using optical depopulation pumping of the metastable on the (3s 4P5/2-3p 4D5/2) transition at 678 nm. At low helium density, 0.24 (+0.16/0.03) of the reionized beam was derived from metastables, implying an ion beam polarization of 24% would be feasible if the metastables were fully polarized. The hyperfine structures of the 3s 4P5/2, 3p 4D5/2 and 3p 4D7/2 states in 19F were measured via laser-induced fluorescence and modulated optical depopulation pumping. Based on these results, a scheme is suggested for polarizing 20F. Thesis work of Thomas E. Cocolios (M.Sc. 2005, McGill University, Montreal, QC) ispartof: Nuclear Instruments and Methods in Physics Research A vol:580 issue:3 pages:1571-1577 status: published

Background: The systematic trend in mean-square charge radii as a function of proton or neutron number exhibits a discontinuity at the nucleon-shell closures. While the established $N=28$ shell closure is evident in the charge radii of the isotopic chains of K through Mn, a similar signature of the $N=20$ shell closure is absent in the Ca region.Purpose: The isotope shift between neutron-deficient $^{36}\mathrm{K}$ and $^{37}\mathrm{K}$ was determined to investigate the change of the mean-square charge radii across $N=20$ in the K isotopic chain.Methods: The $D1$ atomic hyperfine spectra of $^{36}\mathrm{K}$ and $^{37}\mathrm{K}$ were measured using an optical pumping and subsequent $\ensuremath{\beta}$-decay asymmetry detection technique. Atomic rate equations were solved to fit the resonant line shape. The result was compared to Skyrme energy-density functional and shell-model calculations.Results: The isotope shift was obtained as $\ensuremath{\delta}{\ensuremath{\nu}}^{37,36}=\ensuremath{-}139(4)(3)$ MHz. Using a re-evaluated isotope shift, $\ensuremath{\delta}{\ensuremath{\nu}}^{39,37}=\ensuremath{-}264(2)(3)$ MHz, the isotope shift relative to $^{39}\mathrm{K}$ was determined to be $\ensuremath{\delta}{\ensuremath{\nu}}^{39,36}=\ensuremath{-}403(5)(4)$ MHz. The differential mean-square charge radius was then deduced as $\ensuremath{\delta}{\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}}^{39,36}=\ensuremath{-}0.16(5)(8)\phantom{\rule{4pt}{0ex}}{\mathrm{fm}}^{2}$. The Skyrme energy-density functional and shell-model calculations overpredict the experimental values below $N=20$ and underpredict them above $N=20$, and their agreement is marginal.Conclusions: The absence of the shell-closure signature at $N=20$ in the K isotopic chain is understood as a balance between the monopole and the quadrupole proton-core polarizations below and above $N=20$, respectively.

The dynamical behavior of nitrogen impurity in TiO2 was examined microscopically by means of the β-NMR technique. Short-lived radioactive nucleus 12N( I = 1 , T 1 / 2 = 1 1 ms ) was implanted into a single crystal of rutile TiO2 and its NMR was observed at 300–900 K through the β-ray detection. Spin–lattice relaxation due to a fluctuation of the nuclear quadrupole interaction induced by an atomic motion was observed for oxygen substitutional and interstitial lattice sites. The corresponding amplitude of the fluctuation for the substitutional site was found to be much smaller than the static quadrupole field. From this result and the deduced activation energy, we infer that a substitutional 12N atom remains in the site and the observed spin–lattice relaxation is attributed to the motion of some kind of defects. The possibility of interstitial nitrogen diffusion is also discussed.

The electric quadrupole coupling constants eqQ/h of 8B (I π = 2+, T 1/2 = 769 ms) and 13B (I π = 3/2−, T 1/2 = 17.4 ms) in single crystal TiO2 have been precisely measured by the β-NQR technique. The ratios of these Q moments to Q(12B) were determined as |Q(8B)/Q(12B)| = 4.882(32) and |Q(13B)/Q(12B)| = 2.768(24).

The momentum dependences of the nuclear spin polarization P and alignment A of 13B(I π = 3/2+, T 1/2 = 17.36 ms) produced in the 100A MeV 15N + Be collisions have been measured by detecting β-ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some relaxation mechanisms must be take into account. Comparing the signs of the observed alignment of 12B, the sign of the quadrupole coupling constant eqQ of 13B in TiO2 was determined to be positive.

The pure nuclear spin alignments of 8Li and 8B were produced from the nuclear spin polarization applying the β-NMR method. The alignment correlation terms in the β-ray angular distribution were observed to test the G parity conservation in the nuclear β decay.

The β-NMR of short-lived β-emitter 12N(I π = 1+, T 1/2 = 11ms) in a rutile TiO2 single crystal has been measured as functions of temperature and external magnetic field. Atomic motion induced spin lattice relaxation was observed for two known sites, O substitutional and interstitial sites. The data were analyzed in terms of the thermal atomic jump, which suggests that the motion of defects around the substitutional 12N atom for O, and of the interstitial 12N atom are attributed to the spin lattice relaxation. The electric field gradients have shown temperature dependence for both sites, which is probably due to the thermal expansion of rutile.

The g-factor of the exteremely proton-rich nucleus 23Al(T 1/2 = 0.47 s) has been measured for the first time, applying β-NMR technique on this nucleus implanted in Si. The obtained |g| = (1.58 ± 0.2) suggests that the spin of the ground state of 23Al is 5 / 2. The magnetic moment is determined as |μ| = (3.95 ± 0.55) μ N.

Hyperfine interactions of Na isotopes in single crystals have been studied using highly nuclear polarized 20,21,26,27,28Na beams provided by ISAC/TRIUMF. The degree of polarization kept in the crystals, the spin-lattice relaxation times, the electric quadrupole coupling constants and the initial distribution of the populations were measured. Such knowledge is indispensable for the application of the hyperfine interactions in the study of precision measurements such as the nuclear structure through nuclear moments and the fundamental symmetries.

The magnetic moment of 33 Cl ( I π = 3 / 2 + , T 1 / 2 = 2.51 s ) has been re-measured precisely by β -NMR method. The obtained magnetic moment | μ | = 0.7549 ( 3 ) μ N is consistent with the old value 0.7523 ( 16 ) μ N , but is 5 times more accurate. The value is well reproduced by the shell model calculation, μ S M = 0.70 μ N . Combined with the magnetic moment of the mirror partner 33 S, the nuclear matrix elements 〈 l p 〉 , 〈 l n 〉 , 〈 S p 〉 , and 〈 S n 〉 were derived.

The alignment correlation terms in the β -ray angular distributions from spin aligned 8 Li and 8 B have been measured precisely. The difference of these terms between the mirror pair is compared with the prediction. As a result, the G -parity violating induced tensor term is found to be small. The significant contribution from the second-forbidden matrix elements is shown by comparing with the β - α correlation coefficients.

The nuclear moments of 13B(Iπ = 3/2−, T1/2 = 17.36ms) have been re-measured precisely in order to establish the spin manipulation technique for the study of the alignment correlation term in mass system A = 13. From the β-NMR on 13B in Pt, the magnetic moment was determined as |μ(13B)| = 3.1778(5)μN. From the β-NQR on 13B in TiO2, the Q moment has been determined as |Q(13B)| = 36.6(8)mb. We have measured the alignment correlation term α_E for 13B β decay for the first time and obtained a preliminary result as α−(13B) = 0.15(12)%/MeV.

The momentum dependences of the nuclear spin polarization P and alignment A of 12 B ( I π = 1 + , T 1 / 2 = 20.20 ms) [ 13 B ( I π = 3 / 2 − , T 1 / 2 = 17.36 ms)] produced in 100 A MeV 13 C [ 15 N] + Be collisions have been measured by detecting the β -ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some depolarization mechanisms must be taken into account related with the collision process itself. Comparing the signs of the observed alignment of 12 B and 13 B, the sign of the quadrupole moment Q ( 13 B) was determined to be positive.

The alignment correlation term in the β-ray angular distribution from nuclear-spin aligned 20Na(Iπ = 2+, T1/2 = 449.7 ms) has been measured for the first time. A large enhancement of the time component d in the main axial vector current was preliminarily obtained and the higher order matrices j2 and j3 were also evaluated. In order to extract very small G-parity violating induced tensor term, the alignment correlation term of the mirror partner 20F have to be measured.

Collinear laser spectroscopy was performed on an atomic beam of stable 55Mn. An ion beam of 55Mn+ was generated in an ion source, accelerated to 15 keV, and neutralized via charge-exchange reactions with a Na vapor. A long-lived metastable state of Mn I, near-resonantly populated in the charge-exchange process, was investigated via laser probing in addition to a laser excitation from the ground state in Mn I. The relative population of the Mn I metastable state compared to that of the ground state was found to be 0.7 ± 0.3. A theoretical calculation, which included feeding to the ground state and the metastable state from higher-energy excited electronic states populated in the charge-exchange process, agreed with the present result. The deduced A and B hyperfine coupling constants agreed with literature values, where available.

Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was studied at the National Superconducting Cyclotron Laboratory. The nuclei were produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be target. Beam purification was provided by the A1900 Fragment Separator and the Radio Frequency Fragment Separator. The fragments of interest were identified and their decay was studied with the NSCL Beta Counting System (BCS) in conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing, 98Inm and 99In were identified as beta-delayed proton emitters, with branching ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for 89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9 -1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for 101Sn was deduced with higher precision than previously reported. The impact of the newly measured bp values on the composition of the type-I X-ray burst ashes was studied.

The isomeric and $\ensuremath{\beta}$ decays of the $N=Z+2$ nucleus ${}^{96}\phantom{\rule{-0.16em}{0ex}}$Ag were investigated at the National Superconducting Cyclotron Laboratory. A cascade of $\ensuremath{\gamma}$-ray transitions originating from the deexcitation of a microsecond isomer was observed for the first time and was found in coincidence with two previously known transitions with energies of 470 and 667 keV. The isomeric half-life was determined as 1.45(7) $\ensuremath{\mu}$s, more precise than previously reported. The existence of a second, longer-lived microsecond isomer, associated with a 743-keV $\ensuremath{\gamma}$ transition, is also proposed here. Shell model results within the $({p}_{3/2}{p}_{1/2}{f}_{5/2}{g}_{9/2})$ model space, using the jj44b interaction, reproduced level energies and isomeric decay half-lives reasonably well.

The beta-ray angular correlations for the spin alignments of 8Li and 8B have been observed in order to test the conserved vector current (CVC) hypothesis. The alignment correlation terms were combined with the known beta-alpha-angular correlation terms to determine all the matrix elements contributing to the correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2, deduced from the analog-gamma-decay measurement based on the CVC hypothesis. However, there was no consistent CVC prediction for the second-forbidden term associated with the weak vector current. The experimental value for the second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4 or 2.1 \pm 0.5., Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev. C

The isomeric and $\beta$-decay properties of neutron-rich $^{53-57}$Sc and $^{53,54}$Ca nuclei near neutron number $N$=32 are reported, and the low-energy level schemes of $^{53,54,56}$Sc and $^{53-57}$Ti are presented. The low-energy level structures of the $_{21}$Sc isotopes are discussed in terms of the coupling of the valence $1f_{7/2}$ proton to states in the corresponding $_{20}$Ca cores. Implications with respect to the robustness of the $N$=32 subshell closure are discussed, as well as the repercussions for a possible $N$=34 subshell closure., Comment: 17 pages, 17 figures, accepted to Phys. Rev. C