Search

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 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.

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.

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.

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 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.

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.