T.K. Alexander

Nonlinear response of Si detectors for low-Z ions

We report measurements of the relative mean pulse height produced by 1H, 4He, 7Li and 16O ions in Si surface barrier detectors. The data are anomalous in that the pulse height for different ions of the same energy (after window and nonionizing losses are subtracted) increases with atomic number, contrary to observations for fission fragments. A simple model invoking a stopping power dependence of the energy required to create an electron-hole pair is consistent with all experimental data, suggesting that the response of Si detectors is nonlinear with particle energy.

Magnetic moments and half-lives of isomeric states in polonium isotopes

Abstract We have observed small violations of the additivity rule for isomeric two-proton states in 202, 208–210Po. The g-factors of the 110 ns 8+ state in 202Po and of the 24 ns 13 2 − state in 209Po were measured for the first time. The accuracy of relative g-factors which were previously measured has been considerably improved. The static quadrupole moment of 209Bi g.s. is deduced from three E2 transition probabilities in 210Po. The absolute value of Q is ≈ 15% larger than obtained by optical spectroscopy and possible reasons for the discrepancy are discussed.

Quadrupole Moment of a High-Spin Yrast Trap in Gd 147

Static quadrupole interactions of three

Quadrupole moments of yrast isomers in 144, 147, 148Gd

^{147}\mathrm{Gd}

High spin yrast states in N = 126 isotones

isomers in single crystals of hexagonal gadolinium have been observed. The quadrupole moments increase with increasing spin and imply a substantial (oblate) deformation (

Reorientation measurements in even titanium isotopes

\ensuremath{\beta}\ensuremath{\sim}0.2

Yrast isomers and very high spin states in 148, 149, 151, 152Dy and 147Gd

) for the 500-ns high-spin yrast trap.

Measurement of the absolute cross section of the 3He(4He, γ)7Be reaction at Ec.m. = 525 keV

Abstract Isomeric nuclei of 144, 147, 148 Gd were produced by 120, 124 Sn ( 28 Si , x n ) fusion evaporation reactions and implanted into single crystals of Gd. The perturbed angular distribution spectra at various orientations of the crystal axis are dominated by static quadrupole interactions. The ratio of quadrupole moment Q to spin I was determined for the 10 + isomer in 144 Gd, the 13 2 + , 27 2 − and (T 1 2 = 510 ns ) isomers in 147 Gd, and the 9 − isomer in 148 Gd. In addition a tentative value of I = ( 47 2 ± 1) was obtained for the spin of the 510 ns isomer in 147 Gd. The observed quadrupole moments provide the first experimental evidence for the substantial oblate deformation ( β ∼ −0.2) predicted by the deformed independent particle model of Neergard, Dossing and Sagawa for high-spin isomers in 147 Gd. The oblate deformation is observed to increase when the number of valence nucleons (and the isomer spin) increases, and furthermore when the neutron core at N = 82 is broken. The g -factors and quadrupole moments of the 3 − and 10 + core states in 146 Gd have also been deduced.

Quadrupole moment of high-spin yrast trap in /sup 147/Gd

Abstract A comprehensive spectroscopic investigation of yrast levels in three N = 126 isotones, 212 Rn, 213 Fr and 214 Ra, is presented. We report measurements of prompt and delayed excitation functions, γ-γ and X-γ coincidences, g -factors, linear polarizations and angular distributions of γ-rays. Yrast spectra in these nuclei extend to high spin and are rich in isomers. The isomerism and the spin dependence of yrast energies for N = 126 isotones are discussed in terms of excitations of valence protons with and without contributions from the 208 Pb core.

Knight shifts and absolute magnetic moments of (h9/2) n proton states in trans-bismuth nuclei

Abstract The first excited 2 + states in 46,48,50 Ti were Coulomb excited using beams of 35 Cl and 32 S. The results are interpreted in terms of the reorientation effect and yield static quadrupole moments Q( 46 Ti , 889 keV ) = −0.19 ± 0.10 b , Q( 48 Ti , 983 keV ) = −0.22 ± 0.08 b and Q( 50 Ti , 1550 keV ) = −0.02 ± 0.09 b . The B ( E 2) (0 + → 2 + ) values were determined to be 0.107 ± 0.010 e 2 · b 2 , 0.069 ± 0.006 e 2 · b 2 and 0.033 ± 0.003 e 2 · b 2 , respectively. The resu compared with recent Hartree-Fock calculations. The projectile excitation of 32 S was also observed and yielded a limit for the first excited 2 + state of −0.05 Q