T. Minamisono

Determination of the density distribution and the correlation of halo neutrons in 11Li

Interaction cross sections (σ1) and transverse momentum Pt distributions of 9Li fragments in 11Li reactions were measured 1467 using p and d targets at 800A MeV, and Be and C targets at 400A MeV. The density distribution of the 11Li nucleus has been determined for the first time from these σIs. It is confirmed that only a distribution with a long tail (halo) consistently reproduces the observed data. From a combined analysis of Pt distributions of 9Li and of neutrons, the momentum correlation of the two halo neutrons was extracted. It suggests that these neutrons have a strong tendency to move in the same direction.

Density distribution of 8B studied via reaction cross sections

Abstract Reaction cross sections ( σ R ) for 8 B on Be, C and Al targets were measured at energies of 40 A and 60 A MeV. The density distribution of 8 B was studied through a χ 2 -fitting procedure on the σ R including the high-energy data using the optical limit of Glauber theory with assumptions on the enhancement of the σ R at low energies. The result shows a long tail in the density distribution. Large one-proton removal cross sections were also observed to support the existence of a long proton tail consistent with its binding energy.

beta. -ray angular distribution from aligned /sup 12/B and /sup 12/N

The coefficients ..cap alpha../sub minus-or-plus/ in the alignment-correlation terms A..cap alpha../sub minus-or-plus/EP/sub 2/(costheta), in /sup 12/B and /sup 12/N decays have been determined; ..cap alpha../sub -/(/sup 12/B) =+(0.006 +- 0.018) %/MeV, and ..cap alpha../sub +/(/sup 12/N) =-(0.273 +- 0.041) %/MeV. The sign of ..cap alpha../sub +/(/sup 12/N) was determined for the first time, by use of an NMR method and measurements on ..beta..-..gamma.. correlation in aligned /sup 12/N. The (..cap alpha../sub -/-..cap alpha../sub +/) result is consistent with strong conservation of vector currents without second-class currents and the (..cap alpha../sub -/+..cap alpha../sub +/) result gives unique information on the time component of the axial-vector current.

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.

Magnetic moment of proton drip-line nucleus 9C

Abstract The magnetic moment of the proton drip-line nucleus 9 C (I π = 3 2 − , T 1 2 =126 ms ) has been measured for the first time, using the β-NMR detection technique with polarized radioactive beams. The measured value for the magnetic moment is |μ( 9 C )| = 1.3914±0.0005 μ N . The deduced spin expectation value 〈σ〉 of 1.44 is unusually larger than any other ones of even-odd nuclei.

Local lattice expansion of Cu arising from dilute interstitial impurities, β-emitting nuclei 12B and 12N

Abstract Lattice expansions of Cu in the nearest octahedral surroundings of interstitial 12 N were determined to be Δr / r = 0.11 ± 0.02 and 0.13 ± 0.06 respectively using NMR detection. The results are informative to the study of the hyperfine interactions of the impurities in ferromagnetic Ni.

Quadrupole moment of the proton rich β-emitting nucleus 12N

Abstract The quadrupole moment of the β -emitter 12 N( I π =1 + , T 1/2 =11 ms) has been measured to be Q ( 12 N)=+9.8±0.9 mb by use of a modified β -NMR method. The present result is 3 times smaller than the value which was deduced from the photoproduction cross-section of pions on 12 C, while it is twice the shell-model prediction based on the Cohen-Kurath wave functions in the Woods-Saxon potential.

Observation of spin polarization of projectile fragments from 106 A MeV 40Ca+Au collisions☆

Abstract Spin polarization of projectile fragments 37 K and 39 Ca has been observed in 106 A MeV 40 Ca+ 197 Au collisions n ear the grazing angle. The fragment polarization was determined to be positive for points on the high momentum side of the distribution and negative for points on the low momentum side. At the highest energy, the spin polarization follows the same systematics observed at much lower energies, where it is believed that very different reaction mechanisms dominate. A simple fragmentation model explained the observed momentum dependence of the polarization quite well.

Magnetic moments of proton drip-line nuclei13O and9C

The magnetic moments of the proton drip-line nuclei13O(Iπ = 3/2−,T1/2 = 8.6 ms) and 9C(Iπ = 3/2−,T1/2 = 126 ms) have been determined for the first time through the combined techniques of polarized radioactive nuclear beams andβ-NMR detection. The observed magnetic moments are ¦μ(13O)¦ = 1.3891 ±0.0003μN and ¦μ(9C)¦ = 1.3914 ±0.0005μN. Spin expectation values 〈σ〉 are deduced to be 0.76 and 1.44 for13O and9C, respectively. While the 〈σ〉 of13O is consistent with the systematics from isospinT= 1/2 mirror pairs, the 〈σ〉 of9C is unusually large, even far larger than the single particle value, 〈σ〉 = 1.