Precise measurement of the magnetic moment of doubly closed shell + 1 nucleon nucleus17F(I π=5/2+,T 1/2=64.5 s)

Hyperfine interactions of -emitting¹⁷F implanted in single crystals of NaF and CaF₂ were studied. The nuclear magnetic moment of theI =5/2⁺ state was determined with improved precision to be |(¹⁷F;I =5/2⁺,T _1/2=64.5s)|=4.72130±0.00025 µ_N.     

Sign of the quadrupole moment of proton drip-line nucleus 8B

The sign of the quadrupole coupling constant eqQ of ⁸B in ZrB₂ is determined to be positive through the β-delayed α-ray anisotropy measurement combined with the spin manipulation technique by use of the β-NMR. According to the theoretical calculation of the electric field gradient in ZrB₂, the sign of the quadrupole moment of ⁸B is deduced to be positive. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of the driving frequency on the emission characteristics of a radio-frequency glow discharge excitation source boosted by the introduction of a d. c. bias current.

In a radio-frequency-powered glow discharge lamp, a d.c. bias current which is driven by a self-bias voltage can lead to an enhancement of the emission intensities excited by the plasma. The driving frequency of the r.f. plasma is an important parameter to determine the self-bias voltage; lower r.f. frequencies induce greater self-bias voltages. The effects of the bias current introduction on the emission characteristics were compared between a 13.56-MHz plasma and a 6.78-MHz plasma. As a result, the 6.78-MHz plasma offered a better analytical performance, probably due to higher self-bias voltages, if the introduced Ar pressure was optimized. This method was applied to a Mo determination in Fe-matrix alloy samples. At bias currents of 40 - 50 mA, the emission intensities of the Mo I 379.82-nm line were about 10-times larger than those obtained with the conventional plasma when the 6.78-MHz plasma was produced at an r.f. power of 60 W. The detection limit obtained for this calibration was 2.0 x 10(-4) mass % Mo at an 80-W r.f. power and at a d.c. bias current of 68 mA.     

Behavior of Boron Implanted in Semiconductor Si

Using β-NMR with ¹²B nuclei the temperature dependence of the lattice locations of boron implanted in Si is studied. At low temperature almost 100% of the implanted B is in either substitutional site or nonsubstitutional site. Above 260 K, the nonsubstitutional B rapidly becomes undetectable and disappears at a temperature higher than 325 K due to the fast spin-lattice relaxation. Above 450 K, the fraction of substitutional B increases to 100%. These experimental results are consistently explained by the thermal atomic jump and the dissociation of the defect associated with the nonsubstitutional B. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hyperfine Interactions of N Isotopes in TiO2 and Quadrupole Moment of 16N

Hyperfine interactions of ^12,14N in BN(hexagonal) crystal were studied by detecting β-NQR(¹²N) and FT-NMR(¹⁴N). A β-NMR of ¹⁶N (I ^π=2⁻,T _1/2=7.13 s) in MgO crystal was detected to determine the magnetic moment of ¹⁶N to be |μ(¹⁶N:2⁻)|=(1.986±0.001)μ_N. Also, the β-NQR of ^12,16N in TiO₂ crystal were detected to determine |Q(¹⁶N:2⁻)|=(17.9±1.7) mb. An abnormally small effective charge for neutrons is required to account for |Q(¹⁶N:2⁻)|. This revised version was published online in September 2006 with corrections to the Cover Date.     

Benzo­[i]­naphtho­[c,d]­bi­cyclo­[5.4.1]dodecan‐12‐one

In the title compound, penta­cyclo­[11.8.1.1^3,11.0^7,23.0^15,20]­tricosa‐3,5,7,9,11(23),15,17,19‐octaen‐22‐one, C₂₃H₂₀O, the bi­cyclo­[5.4.1]­dodecan‐12‐one moiety takes a rigid conformation in which the seven‐ and eight‐membered rings take chair and boat–boat forms, respectively. The mol­ecule has a non‐crystallographic mirror symmetry perpendicular to the benzene and naphthalene planes.     

Electromagnetic moments of short lived β emitters 21F, 23Mg, 27Si and 39Ca

The β-NMR spectra of ²¹F, ²³Mg, ²⁷Si and ³⁹Ca which were produced in heavy ion collisions and implanted in various crystals have been observed. The magnetic moments of ²¹F and ²⁷Si were determined to be |μ(²¹F)| = 3.9194 ± 0.0012 μ_N and |μ(²⁷Si)| = 0.8653 ± 0.0003 μ_N, respectively. The electric quadrupole coupling constants were determined for the first time to be |eqQ(²¹F in MgF₂)/h|= 9.94 ± 0.09 MHz, |eqQ(²³Mg in MgF₂)/h|= 1.96 ± 0.06 MHz, |eqQ(²⁷Si in Al₂O₃)/h|= 1.90 ± 0.12 MHz, |eqQ(³⁹Ca in CaCO₃)/h|= 0.60 ± 0.04 MHz. From the present eqQ/h, the Q moments were deduced as |Q(²¹F)|= 110 ± 22 mb, |Q(²³Mg)|= 114 ± 3 mb, |Q(²⁷Si)|= 60 ± 13 mb and |Q(³⁹Ca)|= 36± 7 mb. The present data were compared with the theoretical values obtained by the OXBASH shell model code. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reduction of the 1,2,5-thiadiazole ring of 3,6:12,15-di-1,4-benzo[6.6](3,4)-1,2,5-thiadiazolo- and 3,5:11,13-di-1,3-benzo-[6.6](3,4)-1,2,5-thiadiazolocyclophanes. Selective preparation of cis- and trans-[23]cyclophane-1,2-diacetoamide

The effect of the [2.2.2]cyclophane ring structure on the reduction of 1,2,5-thiadiazole ring incorporated in cyclophanes 1a-c and 2a-c was investigated. When reduced by sodium metal in ethanol followed by acetylation, para[2³]cyclophane 1 gave a mixture of the expected cis- and trans-diamides, 3 and 4 , in which 4 was the major product. On the other hand, reduction of 1 with lithium aluminum hydride proceeded in a cis-selective manner and gave 3 as a major product after a treatment of the reduced products with acetic anhydride. The reduction of metacyclophane 2 , which is less strained than 1 , proceeded exclusively in cis-fashion and a subsequent treatment of the reduction product with acetic anhydride gave only cis-diamide 6 .     

Polymer foil applicable to the tilted foil technique

A polymer foil of polyethylene-terephthalate was successfully used for the tilted foil to create nuclear polarization of beta-emitters. The foil was carefully prepared to produce atomic flatness on the surfaces. The resultant smoothness was confirmed with beta-NMR measurements on¹²B and found to be as good as those of carbon foils used previously in the measurements.     

Observation of two-photon above-threshold ionization of rare gases by xuv harmonic photons

We have successfully observed two-photon above-threshold ionization in rare gas atoms (Ar, Xe, and He) by the fifth harmonic (25 eV photon energy) of a KrF laser. Use of the energy-resolved photoelectron counting system together with our laser, providing strong 25 eV radiation at 40-100 Hz, enabled us to detect the very weak single-color two-photon above-threshold ionization signals. Experimental data are in good agreement with our theoretical calculations newly developed along the line of multichannel quantum defect theory.