G. F. Krebs

Inclusive dielectron cross sections in p + p and p + d interactions at beam energies from 1.04 to 4.88 GeV.

Measurements of dielectron production in p + p and p + d collisions with beamkinetic energies from 1.04 to 4.88 GeV are presented. The differential cross section is presented as a function of invariant pair mass, transverse momentum, and rapidity. The shapes of the mass spectra and their evolution with beam energy provide information about the relative importance of the various dielectron production mechanisms in this energy regime. The p + d to p + p ratio of the dielectron yield is also presented as a function of invariant pair mass, transverse momentum, and rapidity. The shapes of the transverse momentum and rapidity spectra from the p + d and p + p systems are found to be similar to one another for each of the beam energies studied. The beam energy dependence of the integrated cross sections is also presented.

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.

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.

QUADRUPOLE MOMENT OF THE PROTON DRIP-LINE NUCLIDE 13O

Abstract The quadrupole moment of the proton drip-line nuclide 13O(Iπ=3/2−,T=3/2,T1/2=8.6 ms) has been determined for the first time by detecting its β-NQR signal following the production of polarized 13O through the projectile fragmentation process in the 16O + Be collision. The quadrupole moment has been determined to be |Q(13O)|=11.0±1.3 mb. The present result together with the quadrupole moment of its mirror partner 13B is compared with the theoretical values obtained by the shell model code, OXBASH, and by the Hartree-Fock calculation with its single proton separation energy taken into account.

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

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 μN and |μ(27Si)| = 0.8653 ± 0.0003 μN, 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.

A fragment separator at LBL for the beta-NMR experiment

Abstract The Beam 44 fragment separator was built at the Bevalac of LBL for NMR studies of beta emitting nuclei. 37K, 39Ca, and 43Ti fragments originating from 40Ca and 46Ti primary beams were separated by the separator for NMR studies on these nuclei. Nuclear spin polarization was created in 39 and 43Ti using the tilted foil technique (TFT), and the magnetic moment of 43Ti was deduced. Fragment polarization was measured for 37K and 39Ca emitted to finite deflection angles. The beam 44 fragment separator in combination with a proper polarization technique, such as TFT or fragment polarization, has been very effective for such NMR studies.

Neutrons from multiplicity-selected La-La and Nb-Nb collisions at 400A MeV and La-La collisions at 250A MeV.

Triple-differential cross sections for neutrons from high-multiplicity La-La collisions at 250 and 400 MeV per nucleon and Nb-Nb collisions at 400 MeV per nucleon were measured at several polar angles as a function of the azimuthal angle with respect to the reaction plane of the collision. The reaction plane was determined by a transverse-velocity method with the capability of identifying charged-particles with Z=1, Z=2, and Z{gt}2. The flow of neutrons was extracted from the slope at mid-rapidity of the curve of the average in-plane momentum vs the center-of-mass rapidity. The {ital squeeze-out} of the participant neutrons was observed in a direction normal to the reaction plane in the normalized momentum coordinates in the center-of-mass system. Experimental results of the neutron squeeze-out were compared with BUU calculations. The polar-angle dependence of the maximum azimuthal anisotropy ratio r({theta}) was found to be insensitive to the mass of the colliding nuclei and the beam energy. Comparison of the observed polar-angle dependence of the maximum azimuthal anisotropy ratio r({theta}) with BUU calculations for {ital free} neutrons revealed that r({theta}) is insensitive also to the incompressibility modulus in the nuclear equation of state. {copyright} {ital 1999} {ital The American Physical Society}

Knight shifts for short-lived beta 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.

Electric quadrupole moment of 25Na

The electric quadrupole coupling constant eqQ/h of 25Na (Iπ = 5/2+, T1/2 = 59.6 s), implanted in a TiO2 single crystal, has been measured by use of the β-NMR technique, to determine the electric quadrupole moment Q. As a result, |eqQ/h| = (44 ± 16) kHz and |Q(25Na)| = (1.0 ± 0.4) mb were determined. From the NMR on 25Na in NaCl, the magnetic moment was determined as |µ| = (3.6832 ± 0.0003) µN