Y. Nakayama

New nuclear quadrupole resonance technique in β-NMR

The β-NMR technique has been modified in order to detect efficiently the nuclear quadrupole effects in the NMR spectra. β-NMR is detected as a function of coupling frequency; all RFs that correspond to the coupling frequency were applied simultaneously.

Magnetic moment of the short-lived β-emitter 23Mg

Abstract The magnetic moment of 23 Mg (I π = 3 2 + , T 1 2 =11.3 s ) has been determined to be |μ( 23 Mg )| = 0.5364±0.0003 μ N by means of a β-NMR detection with recoil polarization obtained through a nuclear reaction. The deduced spin expectation values are in agreement with the systematic behavior of the mirror doublets in the sd shell.

Precise measurement of the quadrupole moment of β-emitting12B

Hyperfine interactions of12B(Iπ,T1/2=21 ms) implanted in the substitutional site of B atoms (stable) in a (single crystal like) BN (hexagonal) was studied by use of a β-NMR detection. For efficient and simple measurements, the conventional β-NMR has been modified as a new nuclear quadrupole resonance technique (NNQR). For the present case with the nuclear spinI=1 the detection efficiency is improved about 30 times compared with the one with the old method. The quadrupole moment of12B was determined precisely as ¦Q(12B; 1+)¦=13.21±0.26 mb.

Electric field gradient in Mg and Zn detected by β-emitters,8Li and12x0392;x0392;x0392;

The quadrupole coupling constants of8Li and12B in hcp Mg and Zn are determined by use of a newly developed nuclear quadrupole resonance technique (NNQR) as ¦eqQ(8Li in Mg)/h¦=3.0±0.3 kHz, ¦eqQ(8Li in Zn)/h¦=33.5±2 kHz, and ¦eqQ(12B in Mg)/h¦=47.0±0.1 kHz. Correspondingly, the electric field gradients at room temperature are deduced: ¦q(8Li in Mg)¦=(3.81±0.39)×1018, ¦q(8Li in Zn)¦=(4.25±0.27)×1019, and ¦q(12B in Mg)¦=(1.47±0.03)×1020, all in V/m2. The experiments are compared with the results of first-principles super-cell band structure calculations which can treat local lattice relaxations around the impurity nuclei. The calculations show that the most favorable location of these light interstitials in hcp Mg is not the octahedral-like sites which have the biggest interstitial volume, but the basal trigonal sites with a local lattice expansion of as big as 30%. Calculated electric field gradients at the impurity nuclei reproduce the experimental values fairly well.

New determination of quadrupole coupling constants of Li isotopes in single crystals LiIO3 andLiNbO3

Quadrupole effects in NMR spectra of8Li(Iπ=2+;T1/2=0.84 s) in LiIO3 andLiNbO3 single crystals have been detected by use of a modified β-NMR. The coupling constants for both crystals are in agreement with known ones. Field gradients in the crystals were measured by detecting pulsed-Fourier transformed NMR of7Li. The quadrupole moments deduced from both samples agree, and|Q(8Li; 2+)|=32.7±0.6 mb has been determined.

Precise measurement of the magnetic moment of17F(I x =5/2+,T 1/2=64.5 s) and its hyperfine interactions in ionic crystals

Hyperfine interactions of β-emitting17F implanted in single crystals of NaF and CaF2 were studied. The nuclear magnetic moment of theTπ=5/2+ state was determined with an improved precision to be |μ(17F;π=5/2+,T1/2=64.5s|=4.72130±0.00025. nm. Isoscalar magnetic moments of the doubly closed shell ±1 nucleon nuclei around mass number 16 were derived and the effective nucleon mass in the nucleus was discussed.

Precise measurement of quadrupole moment of8B by use of a modified β-NMR

The nuclear quadrupole moment of8B(Iπ=2+,T1/2=769 ms) has been determined by use of a modified β-NMR detection as |Q(8B)|=68.3±2.1 mb. A field gradient was obtained in a single crystal Mg at room temperature.

Hyperfine interactions of12B in BN (hexagonal)

Hyperfine interactions of12B(Iπ=1+,T1/2=21 ms) implanted in the substitutional site of B in BN (hexagonal) was studied by detecting β-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.

Giant quadrupole moment andproton halo discovered in8B

The nuclear quadrupole moment of8B(Iπ=2+,T1/2=769 ms) has been determined by use of a modified β-NMR detection as |Q(8B)|=68.3±2.1 mb, which is twice the prediction of the Cohen-Kurath shell model calculation. The anomalous quadrupole moment which is carried mainly by the protons in the nucleus, has been accounted for by the proton halo effect.

Precise measurement of the magnetic moment of doubly closed shell + 1 nucleon nucleus17F(Iπ=5/2+,T1/2=64.5 s)

Hyperfine interactions of β-emitting17F implanted in single crystals of NaF and CaF2 were studied. The nuclear magnetic moment of theIπ=5/2+ state was determined with improved precision to be |μ(17F;Iπ=5/2+,T1/2=64.5s)|=4.72130±0.00025 µN.