Hyperfine interactions of12B in BN (hexagonal)

Hyperfine interactions of¹²B(I =1⁺,T _1/2=21 ms) implanted in the substitutional site of B in BN (hexagonal) was studied by detecting -NMR. In order to measure the quadrupole coupling constant efficiently, we employed a newly developed quadrupole resonance technique (NNQR). The quadrupole moment of¹²B was determined to be |Q(¹²B)|=13.21±0.26 mb.     

Magnetic moment of23Mg

The magnetic moment of the²³Mg (I =3/2⁺, T_1/2=11.3 s), has been determined as |(²³Mg)|=0.5364±0.003 µ_N by use of -NMR detection with the recoil polarization obtained through a low energy nuclear reaction.     

A Possible Nuclear Spin Dewar. Hyperfine Interactions of Short-Lived β Emitter 8Li and 12B in TiO2

It was confirmed by detecting the β-NMR of ¹²B (I ^π=1⁺, T _1/2=20.2 ms) in a TiO₂ (rutile) crystal that the nuclear spin polarization of ¹²B was totally maintained in the crystal as produced through a nuclear reaction before implantation. Two locations, site 1 and site 2, were found with the relative populations 9 and 1, respectively, and the electric field gradients (EFGs) at those sites were obtained to be q(site 1)=+(37.1±0.5)10¹⁵ V/cm², η(site 1)<0.03, q(site 2)=+(185±5)10¹⁵ V/cm² and η(site 2)=0.62±0.02. We also found that about 30% of the initial polarization of ⁸Li (I ^π=2⁺, T _1/2=838 ms) was maintained in the crystal. Since the polarizations of other β emitting nuclei, ^12,16N, ^13,19O, and ⁴¹Sc were also totally maintained in the crystal, the crystal can be a “Spin Dewar” in which many short-lived nuclides can be implanted with their polarizations totally maintained during their lifetimes for the studies not only on the electronic structure of impurities in it but also on the nuclear properties. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine interactions of 19O in TiO2 and quadrupole moments of 13,19O

The electric quadrupole interaction of ¹⁹O(I^π=(5/2)⁺, T_1/2=27.0 s) in TiO₂ single crystal was studied in detail by means of the β-NQR to determine the electric quadrupole moments Q of short-lived β-emitting nuclei ¹⁹O and ¹³O(I^π=(3/2)^-, T_1/2=8.6 ms). Two implantation sites were found for the implanted O nucleus and the quadrupole coupling constants of ¹⁹O at these sites were determined. We observed FT-NMR of the enriched stable isotope ¹⁷O in TiO₂ and obtained the electric field gradient (EFG) at the oxygen substitutional site. With this knowledge, we have determined Q(¹³O)=11.0 ± 1.3 mb and Q(¹⁹O)=3.7 ± 0.4 mb. The present results are compared with the theoretical values calculated by the shell model code, OXBASH and by the Hartree–Fock calculation with the realistic potential. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ab initio calculations of electric field gradients detected by impurities in TiO2, Al2O3 and CaCO3

We present ab initio calculations of electric field gradients (EFGs) at impurity sites in ionic crystals TiO₂, Al₂O₃ and CaCO₃. The electronic structure was calculated self-consistently by the KKR method in the framework of the local spin density approximation of the density functional theory. The system with a single impurity was simulated by the super cell method. It was found that EFGs for the transition metal impurities (Sc, Nb, Cd and Ta) in TiO₂ were well reproduced by the calculations if the charge state of them in TiO₂ was taken into account. The present method was applied to the determination of the implantation sites of N and O nuclei in TiO₂. The calculation of EFGs at a Si impurity in Al₂O₃ and at Ca site in CaCO₃ were used to derive the quadrupole moments of ²⁷Si and ³⁹Ca from their quadrupole coupling constants. This revised version was published online in August 2006 with corrections to the Cover Date.     

Knight shifts for short-lived β emitters in Pt

The Knight shifts K for short-lived β emitters ¹²N and ²⁷Si implanted in Pt have been measured by means of β-NMR technique. The results were K(¹²N in Pt)= +(5.8 ± 2.1)× 10^-4 and K(²⁷Si in Pt)= +(1.4 ± 0.8)× 10^-3. The spin–lattice relaxation time T₁ was measured for ¹²N in Pt. The result was T₁(¹²N in Pt, T=300 K)= 66 ± 8 ms, thus, T₁T= 20 ± 2 Ks. The present Knight shifts are in good agreement with the KKR band structure calculation with local lattice relaxation determined theoretically. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coherent Forward Scattering Spectrometer as a Wavelength Tuning Indicator for Diode Laser Atomic Absorption Spectrometry

A coherent forward scattering spectrometer was used as a wavelength tuning indicator for diode laser atomic absorption spectrometry. Atomic absorption transition of excited argon atoms at 842.46 nm was investigated. Argon atoms were excited in a glow discharge. Coherent forward scattering signal attained maximum at 0.1 T of external magnetic field and at 12 mA discharge current in 266 Pa (2 Torr) of argon. When the lasing wavelength crossed an atomic absorption line, a spike-like signal was observed. When a continuous coherent forward scattering signal was observed, the lasing wavelength was confirmed to approach within about ±3 pm from the absorption transition of argon.     

Momentum dependence of spin polarization for beta emitting nuclei produced through charge exchange reaction at intermediate energy

Hyperfine interactions were studied in the intermetallic compound GdRh₂Si₂ by perturbed angular correlation (PAC) technique using ¹⁸¹Hf(¹⁸¹Ta) probe nuclei. The measurements were performed in the temperature range 15–285 K. The PAC spectra above the antiferromagnetic ordering temperature of the GdRh₂Si₂ compound (T _N ～ 106 K), were analyzed using a model that included only electric quadrupole interactions. The observed major fraction was assigned to the ¹⁸¹Hf(¹⁸¹Ta) probe substituting the Gd atoms. The PAC spectra below Néel temperature were analyzed using combined electric quadrupole and magnetic dipole interactions. The B_hf value at Gd, measured at 15 K was found to be 1.4(1) T which, is smaller, when compared with the values obtained in this compound using other nuclear probes, ¹⁵⁵Gd (B_hf ～ 30 T) and ¹⁴⁰Ce (B_hf ～ 26 T). The present result using ¹⁸¹Hf(¹⁸¹Ta) probe is quite interesting since it shows that the contribution to B_hf at Gd due the host is smaller than other components which contribute to the hyperfine field. The temperature dependence of B_hf shows an anomalous behavior.     

Feruloyl,caffeoyl, and flavonol glucosides from <Emphasis Type="Italic">Equisetum hyemale</Emphasis>

Feruloyl, caffeoyl, and flavonol glucosides were isolated from the stems of Equisetum hyemale L. The structures of the compounds were elucidated as trans-feruloyl-4-β-glucoside (1), cis-feruloyl-4-β-glucoside (2), trans-caffeoyl-3-β-glucoside (3), kaempferol-3-sophoroside (4), kaempferol-3-sophoroside-7-β-glucoside (5), and herbacetin-3-sophoroside-8-β-glucoside (6) based on the spectral evidence.     

Emission characteristics of the dielectronic recombination line of atomic Cu and selectively excited ionic Cu line by resonance charge-transfer collision in a low-pressure laser-induced plasma.

Emisson spectra and time-resolved two-dimensional (2D) emission images of the electron-ion dielectronic recombination (i.e. a reversal process of auto-ionization) line of neutral Cu atoms, the selectively excited Cu ionic line, and normal Cu atomic line were observed for understanding the excitation mechanisms of Cu neutral and ionic lines in a low-pressure laser-induced plasma (LP-LIP) of Ar. From the observations, the number of charged particles around the emitting species seems to increase with increasing Ar pressure. Different time-resolved 2D emission images were observed among the selectively excited Cu ionic line and other Cu emission lines resulting from the different excitation mechanisms of the respective emission lines. Collisions of the second kind and electron-ion recombinations were found to be one of the major excitation mechanisms of Cu in Ar LP-LIP.