Hyperfine Interactions of Short-Lived β Emitters in Pd

The Knight shifts K and the spin-lattice relaxation time T ₁ for the short-lived β-emitters ¹²B and ¹²N implanted into Pd have been measured by means of the β-NMR method. The results show that K depends on temperature. The obtained values of experimental K were compared with theoretical values derived with the KKR method.     

Location of β-emitting12N in V crystal following recoil implantation

Nuclear dipolar broadening in the NMR spectra of β-emitting¹²N implanted in single crystal V was studied as a function of external magnetic field, orientation of the crystal axes relative to the field, and temperature of the sample. The implanted¹²N was located in an interstitial tetrahedral site. The surrounding V atoms nearest to the¹²N were displaced from the regular lattice position; the lattice expansion of large size Δa/a=0.5 was determined.     

Spin-lattice relaxation of 25Al and 28P in Pt

The spin-lattice relaxation times T ₁ for short-lived β emitters ²⁵Al(I?=?5/2, T _1/2?= 7.2 s) and ²⁸P(I?=?3, T _1/2?= 270 ms) in Pt were measured by means of the β-NMR technique. As a result, T ₁[²⁵Al in Pt] = (1.1 $^{+\ 0.7}_{-\ 0.3})$ s and T ₁[²⁸P in Pt] >0.5 s were obtained at temperatures of 17 and 20 K, respectively. The Knight shifts were estimated from the Korringa relation, which were evaluated by comparing to the first principle calculations.     

Two-Photon Laser-Induced Fluorescence Spectra of Argon in a Grimm-Style Glow Discharge Tube

Two-photon excited laser-induced fluorescence (LIF) spectra of argon atom were successfully observed in a Grimm-style glow discharge tube, which has widely been applied to depth profiling of the elemental composition on various film-like samples by emission spectrometry. The LIF signal of an argon atomic line at 641.63 nm was observed when the glow discharge argon plasma was illuminated by a pulsed Ti:sapphire laser radiation of 7–10 mJ/pulse at 753.39 or 795.66 nm without focusing of the laser beam.     

Creation of polarized ultracold neutrons and observation of Ramsey resonance for electric dipole moment measurement

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}(Nd,Pr)-(Tb,Dy,Gd)-(Fe,Co,Al,Cu)-B magnets were heat treated in two different ways and investigated in the temperature range 4.2 to 400 K. After optimal heat treatment intrinsic coercive field _i H _c?= 1640 and 5040 kA/m for room temperature and 10 K was obtained and the temperature coefficient of remanence α?=??0.01 for temperature range 80 to 375 K was found. On basis of magnetic measurements and ⁵⁷Fe Mössbauer spectroscopy, the possible reasons for the increase of _i H _c during multi-step heat treatment are discussed.     

Production of nuclear polarization of unstable nuclei via polarization transfer reactions

To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm². The temporal evolution of the ablation plume was investigated in 800 Pa helium environment. It was found that the observation at 3–5 μs after the ablation at the height of about 2.5 mm are most suited for obtaining higher sensitivity. Using the established conditions, we obtained the limit of detection of the isotope ratio (²³⁵U/²³⁸U) to be 0.01 %. In addition, the limit of detection of elemental abundance of uranium in uranium glass was also evaluated.     

X-ray photoelectron spectroscopic studies on initial oxidation of iron and manganese mono-silicides

Initial oxidation of iron and manganese mono-silicides (FeSi and MnSi) surfaces was studied by X-ray photoelectron spectroscopy (XPS). Clean surfaces of these silicides were prepared by fracturing in an ultra high vacuum, and then the fractured surfaces were oxidized by exposing to high-purity oxygen at pressures up to 1.3 Pa. For the clean FeSi surface, positive chemical shifts of the Fe 2p_3/2 and Si 2p peaks from elemental Fe and Si were 0.5 eV and 0.1 eV, respectively. For the clean MnSi surface, a negative chemical shift of the Si 2p peak from elemental Si was 0.1 eV. Iron on the FeSi surface was oxidized at an oxygen pressure of 1.3 Pa, whereas the silicon was oxidized under the pressure of 1.3 × 10⁻⁶ Pa, indicating that oxidation of silicon occurred prior to that of iron. Manganese and silicon on the MnSi were simultaneously oxidized in the range from 1.3 × 10⁻⁶ Pa to 1.3 × 10⁻³ Pa; however, over the pressure of 1.3 Pa, the oxidation of manganese occurs prior to that of silicon. These oxidation behaviors at low oxygen pressures were similar to those of the FeSi and MnSi fractured in air.     

Spin control and structure of weak nucleon currents in A= 8, 12, 20 and 41

The β-ray angular distributions from purely spin aligned ¹²B and ¹²N were precisely remeasured using a further refined spin-manipulation technique. We determined the amount of a g-parity violating induced tensor form factor in a weak axial vector current as 2M f_T/f_A= +0.22 ± 0.05\ (stat.) ± 0.15\ (syst.) ± 0.05\ (theor.). The result is consistent with the theoretical prediction in the framework of which induced tensor form factor is proportional to u- and d-quark mass difference. To study the g-parity violation in weak nucleon current systematically, we have started to measure the alignment correlation terms of ⁸Li, ⁸B, ²⁰F and ⁴¹Sc. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spin control of 12B and 12N and the axial charge from their β-ray spin-alignment correlations

The spin manipulation technique by use of the β-NMR is further refined, based on the recent thorough studies of hyperfine interactions of ¹²B and ¹²N in Mg. By using this technique, the alignment correlation terms in the β-ray angular distribution of the A = 12 system are precisely measured, so that the axial charge is singled out to be y = 4.66 ± 0.06 (stat.) ± 0.13 (syst.) which shows clear mesonic enhancement over the impulse value. This revised version was published online in August 2006 with corrections to the Cover Date.