Search

The gyromagnetic factor of the low-lying E=251.96(9) keV isomeric state of the nucleus ^{99}Zr was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of J^{π}=7/2^{+}, with a half-life of T_{1/2}=336(5) ns. The isomer was produced and spin aligned via the abrasion-fission of a ^{238}U primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μ_{N} was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd_{5/2} composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.

We report on the operation of co-located ${}^{129}$Xe and ${}^{131}$Xe nuclear spin masers with an external feedback scheme, and discuss the use of ${}^{131}$Xe as a comagnetometer in measurements of the ${}^{129}$Xe spin precession frequency. By applying a correction based on the observed change in the ${}^{131}$Xe frequency, the frequency instability due to magnetic field and cell temperature drifts are eliminated by two orders of magnitude. The frequency precision of 6.2 $\mu$Hz is obtained for a 10$^4$ s averaging time, suggesting the possibility of future improvement to $\approx$ 1 nHz by improving the signal-to-noise ratio of the observation., Comment: 8 pages, 5 figures

We report the results of our theoretical studies of the time-reversal and parity violating electric dipole moment (EDM) of $^{129}\mathrm{Xe}$ arising from the nuclear Schiff moment (NSM) and the electron-nucleus tensor-pseudotensor (T-PT) interaction based on the self-consistent and the normal relativistic coupled-cluster methods. The important many-body effects are highlighted and their contributions are explicitly presented. The uncertainties in the calculations of the correlation and relativistic effects are determined by estimating the contributions of the triples excitations and the Breit interaction, respectively, which together amount to about 0.7% for the NSM and 0.2% for the T-PT interactions. The results of our present work in combination with improved experimental limits for $^{129}\mathrm{Xe}$ EDM in the future would tighten the constraints on the hadronic $\mathcal{C}\mathcal{P}$ violating quantities, and this could provide important insights into new physics beyond the standard model of elementary particles.

We performed a polarized neutron transmission asymmetry measurement utilizing the 139La(n,γ)140La reaction. This measurement involved the use of a recently developed 3He spin filter mounted on the J-PARC MLF beam line number 4 (BL04). The resulting value of the longitudinal asymmetry AL = (11.7 ± 1.1)% was found to be in good agreement with existing values in the literature suggesting that the method by which we polarize the neutron beam is not a significant source of uncertainty. This preliminary work represents a first step toward future measurements of the angular correlation in (n̅,Υ) reactions necessary in the search for enhanced T-Violation in compound nuclei.

The nuclear g factor and quadrupole moment ( Q s ) have been measured for the low-lying isomeric 1 + state of 34Al, using the β-detected nuclear magnetic resonance (β-NMR) and quadrupole resonance (β-NQR) methods. Spin-polarized 34Al isotopes were produced in a one-neutron pickup reaction induced by a 36S beam on a 9Be target at a kinetic energy of 77.5 MeV/nucleon, and were collected with the LISE fragment separator at GANIL. The measured g factor ( | g | in a range of 1.757 ± 0.014 ) and quadrupole moment ( | Q s | = 38 ( 5 ) mb) are in good agreement with shell-model calculations using effective interactions. The similarity between the g factor of 34 m Al and that of 32Al confirms a dominant neutron 2 p 1 h configuration π ( d 5 / 2 ) − 1 ⊗ ν ( d 3 / 2 ) − 1 ( f 7 / 2 ) 2 of 34 m Al. In addition, the enhanced quadrupole moment of 34 m Al relative to that of 32Al suggests that the neutron 1 p 1 h excitation across the N = 20 shell gap introduces extra nucleon–nucleon correlation and deformation.

A new laser spectroscopic method named “OROCHI (Optical RI-atom Observation in Condensed Helium as Ion catcher)” has been developed for deriving the nuclear spins and electromagnetic moments of low-yield exotic nuclei. In this method, we observe atomic Zeeman and hyperfine structures using laser-radio-frequency/microwave double-resonance spectroscopy. In our previous works, double-resonance spectroscopy was performed successfully with laser-sputtered stable atoms including non-alkali Au atoms as well as alkali Rb and Cs atoms. Following these works, measurements with 84−87Rb energetic ion beams were carried out in the RIKEN projectile fragment separator (RIPS). In this paper, we report the present status of OROCHI and discuss its feasibility, especially for low-yield nuclei such as unstable Au isotopes.

We demonstrate spin-exchange optical pumping of 129Xe atoms with our newly made laser system. The new laser system was prepared to provide higher laser power required for the stable operation of spin maser oscillations in the 129Xe EDM experiment. We studied the optimum cell temperature and pumping laser power to improve the degree of 129Xe spin polarization. The best performance was achieved at the cell temperature of 100 ◦C with the presently available laser power of 1 W. The results show that a more intense laser is required for further improvement of the spin polarization at higher cell temperatures in our experiment.

We search for 129Xe EDM by using an active nuclear spin maser. In this experiment, the amplitude of the maser oscillation signal is one of the most important parameters that eventually determine the frequency precision. The amplitude is proportional to the ratio of the transverse spin relaxation time T 2 to the effective longitudinal spin relaxation time $T_{1}^{\ast }$ . In particular, for a spin maser of 3He (a co-magnetometer) for which $T_{1}^{\ast }$ typically reaches ∼50 h, a long T 2 is needed. T 2 depends on the homogeneity of the magnetic field which is applied with coils in order to keep the spins under precession. In the present report, we discuss on the design and construction of a new coil which provided a root-mean square (rms) field gradient of less than 5.0 μG/cm. The result of the field measurement has shown that the field gradient in the cell fulfills the target condition $\sqrt {\langle {(\nabla B_{z})^{2}} \rangle }

The existence of the permanent electric dipole moment of a fundamental particle implies violation of time reversal invariance. The electric dipole moment of a diamagnetic neutral atom is mainly induced by the nuclear Schiff moment. In this study the Schiff moments induced by the interaction which violates parity and time reversal invariance are calculated for various Xe isotopes using the shell-model wave functions. The contributions to the Schiff moment from one-particle and one-hole excitations turn out to be very different from orbital to orbital. It is also found that the contributions from the core excitations are larger than other particle-hole contributions.

Co-magnetometry enables the elimination of systematic errors arising from the long-term drift in the magnetic field, and is essential for a precision measurement of spin precession frequency in experiments searching for electric dipole moment (EDM). $^{131}$Xe nuclear spin maser shows great promise as a co-magnetometer in a Xe EDM experiment, because the systematic error originating from the Xe-Rb interaction, which virtually limits the sensitivity in a case of a $^3$He co-magnetometer, will be cancelled out. The performance of a cell which contains both $^{129}$Xe and $^{131}$Xe was investigated. In the best cell among those fabricated this time, the signal-to-noise ratio in a free induction decay experiment turned out to be large enough for the operation as co-existing $^{129}$Xe-$^{131}$Xe masers.

We provide a general solution to the problem of an infinitely long, hollow cylinder of uniform, linear permeability in the presence of any continuous dc current distribution residing on a concentric cylindrical surface. The solution is expressed in terms of the spatial Fourier components of the applied surface current. Applications of this study include the design of dc magnetic shields and shield-coupled coils, as well as a benchmark for finite-element analysis. Examples involving canonical current structures-loops, solenoids, and saddle-shaped coils-are presented.

Traditional “magic numbers” were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around the magic number of 20, the neutron-rich 39Cl isotope provides a good test case for the study of the quantum-state evolution across the major shell. In the present work, the negative parity states in 39Cl are investigated through the β decay spectroscopy of 39S. Newly observed γ transitions together with a new state are assigned into the level scheme of 39Cl. The spin parity of 5/2− for the lowest negative parity state in 39Cl is reconfirmed using the combined γ transition information. These systematic observations of the negative parity states in 39Cl allow a comprehensive comparison with the theoretical descriptions. The lowest 5/2− state in 39Cl remains exotic in terms of comparisons with existing theoretical calculations and with the neighboring isotopes having similar single-particle configurations. Further experimental and theoretical investigations are suggested.

We are developing a new nuclear laser spectroscopic technique for the study of nuclear structure that can be applied to short-lived low-yield atoms with unstable nuclei. The method utilizes superfluid helium (He II) as a trapping medium for high-energy ion beams. A liquid helium cryostat with optical windows is a key apparatus for this type of experiment. We describe the design and the performance of the cryostat which is developed for the present project.

We have been developing a novel nuclear laser spectroscopy method “OROCHI” for determining spins and moments of exotic radioisotopes. In this method, we use superfluid helium as a stopping material of energetic radioisotope beams and then stopped radioisotope atoms are subjected to in situ laser spectroscopy in superfluid helium. To confirm the feasibility of this method for rare radioisotopes, we carried out a test experiment using a 85 Rb beam. In this experiment, we have successfully measured the Zeeman resonance signals from the 85 Rb atoms stopped in superfluid helium by laser-RF double resonance spectroscopy. This method is efficient for the measurement of spins and moments of more exotic nuclei.

In order to investigate the structure of exotic nuclei with extremely low yields by measuring nuclear spins and moments, a new laser spectroscopy technique – “OROCHI” (Optical Radioisotopes Observation in Condensed Helium as Ion-catcher) has been proposed in recent years. The feasibility of this technique has been demonstrated by means of a considerable amount of offline and online studies of various atoms in superfluid helium. For in-situ laser spectroscopy of atoms in He II, trapping atoms in the observation region of laser is a key step. Therefore, a method which enables us to trap accelerated atoms at a precise position in He II is highly needed for performing experiment. In this work, a technique making use of a degrader, two plastic scintillators and a photon detection system is established for checking the stopping position of beam based on the LISE++ calculation. The method has been tested and verified by on-line experiments with the 84 , 85 , 87 Rb beam. Details of the experimental setup, working procedure and testing results of this method are presented.

A novel method to produce spin-aligned rare-isotope (RI) beam has been developed, that is the two-step projectile fragmentation method with a technique of dispersion matching. The present method was verified in an experiment at the RIKEN RIBF, where an RI beam of 32Al with spin alignment of 8(1) % was successfully produced from a primary beam of 48Ca, with 33Al as an intermediate nucleus. Figure of merit of the present method was found to be improved by a factor larger than 50 compared with a conventional method employing single-step projectile fragmentation. ispartof: pages:47-51 ispartof: Hyperfine Interactions vol:220 issue:1 pages:47-51 ispartof: 4th Joint International Conference on Hyperfine Interactions / International Symposium on Nuclear Quadrupole Interactions (HFI/NQI) location:Beijing, China date:10 Sep - 14 Sep 2012 status: published

Polarized UCNs have been created by selecting only one spin state passing through a magnetized Fe foil. Typical degree of polarization was about 90 %. The polarization relaxation time in the prototype Ramsey cell was \(T_1 =1100^{+800}_{-400}\) s. Clear Ramsey resonance spectra have been observed for two precession time settings, tc = 100 ms and 30 s. The transverse relaxation time T2 was about 50 s.

The present status of an active spin maser which is being developed for an experimental search for 129Xe atomic electric dipole moment (EDM) is presented. In order to realize the long term stability of maser frequency, systematic effects for the spin maser operation were investigated. The correlations in the maser frequency with the solenoid current, the environmental field and the cell temperature were found. With the solenoid current and environmental field being stabilized and the cell temperature lowered, a frequency precision of 7.9 nHz has been achieved for the maser operation.

We report on a new measurement of the g factor of the (13/2(+)) isomeric state in the neutron-rich nucleus Cu-69. This study demonstrates the possibility of obtaining considerable nuclear spin alignment for multi-quasiparticle states in single-nucleon removal reactions. The time-dependent perturbed angular distribution (TDPAD) method was used to extract the gyromagnetic factor of the (13/2(+)) [T-1/2 = 351(14) ns] isomeric state of Cu-69. Its g factor was obtained as g(13/2(+)) = 0.248( 9). The experimentally observed spin alignment for the state of interest was deduced as A = -3.3(9)%.

A 129Xe nuclear spin oscillator with an artificial feedback was constructed, and detailed studies were conducted on its performance, focusing on the frequency stability. As a result, the major sources of drift of the precession frequency in the present spin oscillator setup were identified to be drifts of a solenoid current and an environmental magnetic field. By introducing stabilization systems for the current and the environmental field, which yielded improvements by one order of magnitude on the solenoid current and by a factor of three on the environmental field, a frequency precision of 7.9 nHz was obtained for a one-shot measurement of 3 × 104 s duration. We found, however, that the Allan deviation leveled off at around 30 μHz, indicating a strong need for the precision monitor of the experimental conditions represented by magnetometry. The frequency stability of the spin oscillator is discussed in relation to an experimental search for an electric dipole moment of the 129Xe atom.

Electric quadrupole moment Q of the Al 33 ground state has been measured by means of β-NMR spectroscopy using a spin-polarized Al 33 beam produced in a projectile fragmentation reaction. The obtained Q moment, | Q exp ( 33 Al ) | = 132 ( 16 ) e mb , shows a significant excess from the prediction of shell model calculations within the sd shell. The result indicates sizable admixing of pf intruder configurations in the ground state, demonstrating that the N = 20 shell closure certainly erodes in Al 33 , a nucleus located on the border of the island of inversion. Comparison was made with predictions of the Monte Carlo shell model, and also a particle-vibration coupling model treating the neutron pairing correlations in the ground state of Al 33 . Again, a significant admixture of pf intruder configurations to the Al 33 ground state was needed in both theoretical approaches to explain the observed large Q.

We have constructed a 129Xe nuclear spin oscillator which executes a self-sustained oscillation through an external feedback loop with optical detection of nuclear spin. The oscillator is capable of operating at frequencies much lower than the conventional nuclear spin maser. A method for efficient optical detection of spin has been developed and applied to the nuclear spin oscillator, and the frequency characteristics of the oscillator at low frequencies has been investigated. The spin oscillator was operated at frequencies 2.5–36 Hz. The frequency performance of the oscillator is discussed in relation to a planned search for an atomic electric dipole moment taking advantage of the present oscillator scheme.

A neutron EDM measurement with a comagnetometer is discussed. For magnetometry, polarized xenon atoms are injected into a cylindrical cell where a cylindrically symmetric magnetic field and an electric field are applied for the EDM measurement. The geometric phase effect (GPE), which originates from particle motion in a magnetic field gradient, is analyzed in terms of the Dyson series. The motion of the xenon atom is largely suppressed because of a small mean free path. The field gradient is controlled by means of NMR measurements, where the false effect of Earthʼs rotation is removed. As a result, the GPE is reduced below 10 − 28 e cm .

Immediately after the GeV-implantation of 57Mn nuclei produced by the RIKEN-RIBF facility, 57Mn/57Fe Mossbauer spectra in Si-solar cells are measured under light illumination. Comparing with the spectrum of p-type multi-crystalline-Si, the broad spectra of the solar cell under operation can be analyzed as a superposition of interstitial and substitutional Fe components with different charge states. The charge states of Fe impurities are created by the excess carrier injection followed by a directional carrier flow in the p-n junction. The present results provide us a possibility to clarify the carrier trapping process at the Fe impurities in Si-solar cells.

We have been developing a high sensitivity atomic magnetometer for atomic EDM experiments using a lowfrequency nuclear spin maser. In the developed nuclear spin maser of 129 Xe, suppression of drift and fluctuation in the magnetic field is one of the important issues. The magnetometer being developed for spin maser EDM experiments utilizes the nonlinear magneto optical rotation (NMOR) e_ect in Rb atomic vapor. The enhancement of the optical rotation in a small magnetic field relies on the long spin-coherence time of Rb atoms in a vapor cell. The NMOR spectrum was measured by using fabricated Rb cells coated with an anti-relaxation material. The NMOR spectrum dependence on laser frequency, cell coating, and laser beam diameter were investigated. The magnetic sensitivity at present is 0:2 μG/√Hz from observed NMOR and noise spectra.

A gradient DC magnet is designed using 3D magnetic field analysis code. This magnet, referred to as a B0 magnet, is one of the key elements of a time-focusing device for ultra-cold neutrons (UCNs) based on a radio frequency gradient flipper – a so-called rebuncher. The magnet generates a guide and a potential field that interacts with the magnetic moment of UCNs and its main body comprises a C-shaped yoke made from iron. A field gradient is generated by a pole arrangement that includes an anisotropic inter-pole, which causes the fringe field to be uniform in the longitudinal direction even when the pole gap distance changes. The designed magnet has the following properties: (1) a maximum B-field of 10 kGauss, decreasing to 2 kGauss at a longitudinal distance of 25 cm, with a gradient of less than 400 Gauss/cm, (2) variations in the fringe field along the y direction is less than 4% over a range of − 3 cm≤ y ≤ 3 cm at any z position in the spin-flipping region. Tracking simulations show that the B0 magnet is capable of accepting UCNs in the velocity range 2.3∼3.3 m/s.

Frequency characteristics of a 129 Xe nuclear spin maser was studied, which is under development at Tokyo Institute of Technology for the search for a permanent electric dipole moment in diamagnetic 129 Xe atom. Drifts in the solenoid current and cell temperature were found to be the most influential factors on the maser frequency. From correlation coefficient analysis, there seem to exist other origins of frequency fluctuation, such as phase drifts in the maser oscillation. In order to improve the stability of the maser frequency, the intensity of the pumping laser required to fully polarize 129 Xe nuclei was evaluated. Construction of a polarization assessment system for 129 Xe gas cells and development of a new scheme of current stabilization are also remarked.

A nitrogen vacancy (NV) center in diamond is studied as a solid state spin system realizing quantum information processing. In order to make such a system work as a qubit or a quantum memory, it is essential to have a full knowledge of interactions between the spins. Focusing on the properties of the NV center, of which the electron spin is experimentally accessible and can be transferred to a single nuclear spin, dynamics and interactions between the single spins can be known to the full extent. We aim at measuring a change of state of the single nuclear spin upon interaction with single NV electron spin in a short time interval. It corresponds to the weak measurement initiated by Aharonov et al., and through such a measurement the hyperfine interaction between the NV electron spin and the nuclear spin can be determined. As a first step toward such an experimental application of the weak measurement scheme, we carried out the detection of single NV centers with confocal laser microscopy and the measurement of the second-order autocorrelation function. We undertook an optically detected magnetic resonance (ODMR) to manipulate and read out the electron spin state and evaluated the static magnetic field applied at the single NV center from obtained ODMR spectra.

The development of a nuclear spin oscillator system, namely a spin maser with an external feedback, for use in the search for 129Xe atomic EDM is presented. By introducing a new current source for the B0 field solenoid, drifts in the maser frequency were remarkably suppressed. This in turn clearly brought out the correlation between the maser frequency and the environmental field. Correcting for the effect of the environmental field, the frequency precision of 5 nHz in the measurement time of 45,000 s was attained. Origins of the remaining drifts in the maser frequency are now under investigation.

We have been developing a new nuclear laser spectroscopic method “OROCHI” for determining spins and moments of exotic RIs. It is the method based on the combination of superfluid helium as a stopper of radioactive isotope (RI) beam and in situ laser spectroscopy of RI atoms. This unique method will enable us to measure nuclear spins and electromagnetic moments of extremely low yield RI (less than 1 particle per second). For applying this method to stable Ag and Au isotopes, we have measured optical absorption spectra of these elements. Optical pumping of those atoms has also been attempted with pumping lasers tuned to the measured absorption lines. Details of this laser spectroscopy method in He II “OROCHI” and the development for applying OROCHI to Ag and Au atoms are presented.

Electric quadrupole coupling constant eqQ/h of the extremely proton-rich 23Al (I π = 5/2 + , T 1/2 = 0.47 s) nucleus implanted into an Al2O3 single crystal has been measured for the first time, using the β-ray detecting nuclear quadrupole resonance method (β-NQR) in a high magnetic field. As a preliminary result, the quadrupole coupling constant was determined as |eqQ/h(23Al) | = 2.66±0.77 MHz. Using the quadrupole coupling constant of 27Al in Al2O3 as a reference, the Q moment of the ground state of 23Al was extracted as |Q(23Al)| ~ 160 mb, which is well explained by the shell model calculation in the sd-shell model space with the USD interaction.

External bending stress was applied to a 57Fe-doped n-type silicon wafer, and transmission Mossbauer spectra were measured at room temperature in order to observe directly stress induced diffusion of 57Fe atoms in the silicon matrix. As the stress is increased up to 23 MPa, the resonance area of the substitutional Fes component is found to decrease by more than 30%. In addition, a line broadening can be clearly seen in the interstitial Fe $_{\rm i}^{0}$ component, corresponding to a jump frequency of 106 s − 1. This diffusion process is interpreted to be due to the fast jumps between interstitial sites, following a formation jump of interstitial Fe $_{\rm i}^{0}$ from substitutional Fes.

The β-NMR study of short-lived nucleus 58Cu (I π = 1 + , T 1/2 = 3.2 s) in Si has been performed. Spin polarization of 58Cu induced by the charge exchange reaction of 58Ni was observed in Si at 15 K. The 58Cu magnetic moment $|\upmu[^{58}\mbox{Cu}]| = (0.46 \pm 0.03)\upmu_{\rm N}$ deduced from the β-NMR spectrum is consistent with the previous results on the laser spectroscopy. The present result shows that the 58Cu nucleus is promising as a new nuclear probe for the microscopic study of Cu impurities in Si.

Nuclear moment studies on nuclei situated far from the β-stability line, performed by taking advantage of the projectile fragmentation reaction, are reviewed. A method to produce spin polarization/alignment in the projectile fragments was developed and utilized for the β-NMR/NQR measurements. Several new findings in nuclear structure physics were obtained from the nuclear moment experiments done with these techniques.

Viewing a nucleus as a collection of independent particles has been, since the spin-orbit force was introduced [1], a successful way of understanding major nuclear properties that are governed by a particular series of numbers—the magic numbers. Such properties result from the bunching of the single-particle orbits, or the existence of nuclear shells. About half a century after, however, the present-day studies of nuclei far from the β stability line reveal that the nuclear shells may evolve [2]: As the N/Z ratio increases, the single particle orbits migrate upward or downward in energy depending on their j = l ± 1/2 character. As a result the decisive role played by one orbit (the valence orbit) is taken over by another, and in some cases the nuclear deformation sets in even in a nucleus whose N or Z number is a (heretofore) magic number. In such a situation, the nuclear moments, namely the magnetic dipole moments μ and electric quadrupole moments Q, serve as very useful indicators for alterations in nuc...

The electric quadrupole coupling constant of the 31 Al ground state is measured to be ν Q = | e Q V z z h | = 2196 ( 21 ) kHz using two different β -NMR (Nuclear Magnetic Resonance) techniques. For the first time, a direct comparison is made between the continuous rf technique and the adiabatic fast passage method. The obtained coupling constants of both methods are in excellent agreement with each other and a precise value for the quadrupole moment of 31 Al has been deduced: | Q ( Al 31 ) | = 134.0 ( 16 ) mb . Comparison of this value with large-scale shell-model calculations in the sd and sdpf valence spaces suggests that the 31 Al ground state is dominated by normal sd-shell configurations with a possible small contribution of intruder states. The obtained value for | Q ( Al 31 ) | and a compilation of measured quadrupole moments of odd- Z even- N isotopes in comparison with shell-model calculations shows that the proton effective charge e p = 1.1 e provides a much better description of the nuclear properties in the sd-shell than the adopted value e p = 1.3 e .

We have been working on the development of a new technique of atomic-beam resonance method to measure the nuclear moments of unstable nuclei. In the present study, an ion-guiding system to be used as an atomic-beam source have been developed.

A nuclear spin maser of a new type, that employs a feedback scheme based on optical nuclear spin detection, has been fabricated. The spin maser is operated at a low static field of 30 mG by using the optical detection method. The frequency stability and precision of the spin maser have been improved by a highly stabilized current source for the static magnetic field. An experimental setup to search for an electric dipole moment (EDM) in 129Xe atom is being developed.

The online time-differential perturbed angular correlation (TDPAC) method was applied to a study of the physical states of a probe 19F, the β− decay product of 19O (t1/2 = 26.9 s), implanted in highly oriented pyrolytic graphite. The observed magnitude of the electric field gradient at the probe nucleus, ∣Vzz∣ = 2.91(17) × 1022 V m−2, suggests that the incident 19O atoms are stabilized at an interlayer position with point group C3v. Exhibiting observed TDPAC spectra having a clear sample-to-detector configuration dependence, we demonstrate the applicability of the present online method with a short-lived radioactive 19O beam.

At the RI-beam facility of the RIKEN, 57 Mn/ 57 Fe isotopes are separated and implanted into n-type FZ-Si (6 × 10 16 As/cm 3 ), and subsequently the atomic jump processes of 57 Fe in the Si matrix are observed by Mossbauer spectroscopy on a time scale of 100 ns between 330 and 1200 K. The spectra consist of two components due to "interstitial Fe" and "substitutional Fe", both of which yield the same isomer shifts as those reported in p-type Si, showing long-range diffusion with increasing temperature. The spectra are compared with those simulated from a theoretical model.

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.

A new method to produce spin-polarized radioactive nuclear beams has been developed, which takes advantage of the low-energy transfer reaction in inverse kinematics. The method provides beam energies of a convenient range so that they may be implanted in a thin stopper, yet allowing the stopper to be spatially separated from the production target. The presence of polarizations of sizes at least \(\left|P\right|\sim 0.5 \%\) has been confirmed for a 17N beam obtained from 9Be(18O,17N) reaction at \(\theta_{\rm Lab} \sim -1.7\,^{\circ}\).

The time-differential perturbed angular correlation (TDPAC) method was applied to a study on the behavior of 140Ce atoms implanted in highly oriented pyrolytic graphite (HOPG). Exponential-type gradual attenuation of the directional anisotropy of the relevant γ-ray cascade was observed in the perturbation patterns. From temperature dependence of the relaxation rate, a thermally activated dynamic motion of the probe atoms was suggested.

The electric quadrupole moment Q for the ground state of 32Al has been measured using the β-NMR technique. Spin-polarized 32Al 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 quadrupole moment was deduced from the measured quadrupole coupling constant. The obtained value, | Q ( Al g.s. 32 ) | = 24 ( 2 ) mb , is remarkably small as compared with other Al isotopes, but is well explained by shell model calculations within the sd shell. The present result indicates that 32Al has a normal sd-shell structure, in contrast to the neighboring N = 19 isotone 31Mg for which a strongly deformed intruder ground state has been reported to occur.

Based on the technique of fragment‐induced spin polarization combined with the β‐NMR method, a series of experiments has been carried out at RIKEN for the nuclear‐moment measurement of light unstable nuclei. The measurement will be extended further in the RIKEN RIBF project, where radioactive‐isotope beams in the medium‐ and heavy‐mass regions will be produced at higher energies and with higher intensities compared with the RARF facility. Measurements of the isomeric‐state nuclear moments of unstable nuclei will be started with BigRIPS by utilizing fragment‐induced spin‐orientation phenomena. Also, an upgrade program of the existing fragment separator RIPS is proposed in the phase‐II program of RIBF. Then, intense beams will be delivered to RIPS at E ∼ 115 A MeV. This energy region is useful, not only because spin orientation is produced in the PF reaction but also they can be implanted into sample materials with limited thickness.

The development of techniques to produce low‐energy spin‐polarized radioactive nucleon beams (RNBs) is reported. It employs the inverse‐kinematics reactions of law energy heavy‐ion beams for the RNB production with in‐flight separator. Some plans of research are discussed that apply these well‐focused, conveniently energetic spin‐polarized RNB to nuclear structure physics and material science.