Akira Mizobuchi

Quadrupole Effects in NMR Spectra on Short-Lived β-Radioactive Nuclei, 12B and 12N

Quadrupole effects in NMR on 12 B( T 1/2 =20 ms) and 12 N( T 1/2 =11 ms) have been investigated by using the polarized nuclei produced and implanted through nuclear reactions and the resultant asymmetric β decay. The implantation media were polycrystalline bcc metals (Nb, Mo, Ta and W), TiB 2 and ZrB 2 . To increase the observable effects in NMR, a frequency-modu-lated r.f. field was employed. The spectra in bcc metals show the characteristics of quadrupole interaction for nuclear spin \(I{=}1\hslash\), and the determined coupling constants depend largely on the periodic groups of the related elements. The spectra in the bcc metals together with those in the fcc metals (Al, Cu, Pt and Au) indicate that the major implanted sites are interstitial. From the results on TiB 2 and ZrB 2 and the known values on 11 B, the ratio of quadrupole moments is determined as | Q ( 12 B)/ Q ( 11 B)|=0.42±0.04, and the moment of 12 B is deduced to be | Q ( 12 B)|=0.017 1 ±0.001 6 b.

Magnetic Moment of F17 – Nuclear Magnetic Resonance by Polarization Following O16 (d, n) F17 Reaction –

The nuclear magnetic resonance of F 17 ( T 1/2 =66 sec) has been observed using the polarization of recoil nuclei produced by the reaction O 16 ( d , n ) F 17 and the β-decay anisotropy as the indicator of the polarization. The accomplishment of the experiment was essentially due to the persistence of the polarization by specific experimental methods, i.e. , the use of a strong magnetic field (\({\gtrsim}5\) kG) in the direction of polarization and the use of pure CaF 2 crystals as the stopping material of recoil ions. The observed asymmetry of β-counting was about 2% and a spin relaxation time T 1 comparable to the half-life of F 17 was observed. The value obtained of the magnetic moment of F 17 is µ=4.7224±0.0012 nm with the diamagnetic correction.

Quadrupole moment of the β-emitter 17F

The quadrupole effect in the NMR of 17F(Iπ = 52+, T12 = 66 s) in a MgF2 single crystal has been investigated. Production and implantation of polarized 17F through the 16O(d, n) reaction and the resulting asymmetric β-decay were utilized. The quadrupole coupling constant is determined to be |eqQ/h| = 8.41 ± 0.24 MHz with η = 0.32 ± 0.02 at room temperature. No appreciable temperature dependence of eqQ is found from 77 K up to 770 K. Using previously known results, the following ratios of the quadrupole moments are obtained; |Q(17F, 52+)| : |Q(18F∗, 5+)| : |Q(19F∗, 52+| : |Q(20F, 2+)|= 1 : (1.33 ± 0.08) : (1.24 ± 0.06) : (0.69 ± 0.02). The additivity relation of Q between 17F, 17O, and 18F∗ is discussed.

Magnetic substate populations of product nuclei in the 11B(d, p)12B reaction

Abstract Magnetic substate populations of product nuclei in the 11 B(d, p) 12 B reaction have been measured in an energy range E d = 1.3−3.0 MeV at recoil angles of θ R = 55°, 515° and 27°−37°. A static magnetic field (3 kG) was applied normal to the reaction plane to keep the nuclear orientation. Quadrupole effects on the implanted 12 B in Ta were utilized to perturb the Zeeman splitting. NMR transitions were induced, and detected by the asymmetry change in the β-decay of 12 B. From this information, the magnetic substate populations were determined, for the unique assignment of which the sign of the quadrupole interaction had to be known. For this purpose, a p−γ angular correlation was measured, which determined the alignment of the first excited state of 12 B. A comparison of the present result with theoretical predictions is given, together with the resultant information about j -mixings in the 12 B states.

Use of ion-induced X-rays to locate ion-implanted impurities in gallium arsenide

Abstract Ion channeling and ion-induced X-ray measurements have been performed to study the lattice locations of S and Mn implanted in GaAs single crystals. The signal-to-background ratios for S X-rays using various beam types and additional absorbing Befilters were compared in order to obtain a good signal-to-background ratio. The effect of channeling on the background radiation due to the bremsstrahlung from secondary electrons was investigated. About 100% of S atoms implanted at 200 °C were located on substitutional sites while S atoms implanted at room temperature were located on sites slightly displace from lattice sites after annealing 800°C. About 100% of Mn atoms implanted at 200°C were located on substitutional sites.

Polarization of 12B in deep-inelastic heavy-ion reaction 100Mo(14N, 12B)

Abstract Spin polarization of 12 B was measured for 100 Mo( 14 N, 12 B) at E i ( 14 N ) ≅ 200 MeV as a function of Q value down to Q ⋍ −150 MeV , and was found anti-parallel to k f × k i in the deep-inelastic region. The data together with those at lower incident energies show a systematic trend in Q -value dependence of the polarization.

Precision Lifetimes of Positron Emitters, 25Al, 29P, 33Cl, and 41Sc, and ft Values of Mirror β Decays

Half lives of positron decays of 25 Al, 29 P, 33 Cl, and 41 Sc, have been determined to be (7.177±0.023)s, (4.149±0.005)s, (2.513±0.004)s, and (0.591±0.005)s, respectively. Each object activity was produced at a resonance energy of the proton-capture reaction to minimize the contamination due to other activities. The f t values of mirror β decay for 11≤A≤41, which were calculated by using a refined wave function of electron and the recent data, are presented.

GAMMA RAYS FROM SEVERAL ELEMENTS BOMBARDED BY 10 AND 14 Mev PROTONS

Gamma ray spectra and intensities from C, O, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Cu, Ag, Cd, Sn, Pt, Au and Pb bombarded by 10 and 14 MeV protons have been studied. For C, O, Mg, Si and Ca, most of the gamma rays could be attributed to the inelastic scattering. New levels at 7.08 and 8.13 MeV are suggested in 40 Ca.

Lattice-Site Locations of Tin and Antimony Implanted in Gallium Phosphide

The lattice locations of Sn and Sb atoms implanted in GaP single crystals have been studied as a function of implantation temperature by means of ion channeling and ion-induced X-rays. Angular scans through the major axes were performed to distinguish two types of substitutional sites in GaP. For the implantation at 400°C, about 80% of Sn atoms and 100% of Sb atoms were located on Ga- and P-substitutional sites, respectively. Sn and Sb atoms implanted at room temperature were found to be on off-lattice sites even after annealing at 700°C. An implantation annealing stage for lattice location and lattice disorder was observed in the temperature range from 200°C to 250°C.

Measurement of ejectile polarization in heavy ion reactions via beta-ray asymmetry

Abstract A method for measuring spin polarization of ejectiles in heavy ion reactions is presented, which capitalizes the asymmetry in the angular distribution of β-rays from the ejectile. Incorporating the NMR technique the detection of β-ray asymmetry proves to be indeed a sensitive and reliable way to determine polarization when applied to short-lived β-emitting products with high Q β -values. The method was used to investigate the polarization of the product 12 B as a function of Q -value of the reactions induced by heavy ions at energies well above the Coulomb barrier. Sizeable polarization was observed. The results show that this method provides us with useful information in investigating the heavy ion reaction mechanisms. The polarization observed in these reactions implies the possibility of a wide variety of applications.