Bound states of quarks

A ‘year-2001’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-1992’ set, a major revision of the value or a considerable improvement of the accuracy is reported for 6 3Li, 7N, 19 9F (197 keV, I = 5/2), 11Na, 13Al, 21Sc, 22Ti, 26Fe (14 keV, I = 3/2 Mossbauer state), 31Ga, 32Ge, 77 34Se (250 keV, I = 5/2 state), 35Br, 36Kr, 37Rb, 39Y, 40Zr, 100 45Rh, 50Sn (24 keV, I = Mossbauer state), 53I, 54Xe, 55Cs and 83Bi.

Spectroscopic nuclear quadrupole moments

We ask whether the universe can be a patchwork consisting of distinct regions of matter and antimatter. We demonstrate that, after recombination, it is impossible to avoid annihilation near regional boundaries. We study the dynamics of this process to estimate two of its signatures: a contribution to the cosmic diffuse γ-ray background and a distortion of the cosmic microwave background. The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter-antimatter symmetric universe is empirically excluded.

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A Matter-Antimatter Universe?

A description of high-spin phenomena in atomic nuclei is presented from both the experimental and theoretical points of view. The characteristic features of collective nuclear motion, such as rotational bands, band crossings, and backbending, as well as noncollective aspects, like high-spin isomers and irregular decay patterns, are discussed in detail. Recent achievements of the cranking model including the independent quasiparticle and the shell correction methods are reviewed. Changes in the structure of nuclei excited up to the highest possible angular momenta are analyzed; in particular, angular momentum alignment effects, shape changes, possible phase transitions, and sudden rearrangements in the single-particle structure are discussed. Phenomena related to the nuclear quasicontinuum spectra are also examined.

High-spin phenomena in atomic-nuclei

Theory of finite Fermi systems and application to the lead region

Effective quadrupole charges in the lead region

Excited nuclear levels in doubly even Xe isotopes populated in (α, 2n) reactions

The absorption of stoppedπ− in181Ta and209Bi has been investigated by studying prompt and delayedγ-ray spectra. Absolute cross-sections for the yield of isotopes per capturedπ− in (π−, xn) reactions, as well as the relative probability of populating nuclear states of different spins have been measured for the hafnium and lead isotopes, respectively. A spin as high as 20 has been observed in the production of204Pb. The ground-state rotational bands of the hafnium isotopes are excited to spin values up to 16. Neutron multiplicities as large as 15 have been observed for both targets. A neutron multiplicity of ≃8 is most probable for both tantalum and bismuth targets.

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High spin states and neutron multiplicities after pion capture in181Ta and209Bi

Proton-antiproton annihilations at rest into π0ω, π0η, π0γ, π0π0, and π0η′

Using the 204Hg(α,2n) reaction and the pulsed beam of our 225 cm cyclotron, we have been able to localize the 12+ and 10+ states of the (i13/2)-2 configuration in 206Pb at the energies 4 027.2 and 3 957.6 keV, respectively. It has been possible to determine the partial E2 transition probability for the 12+ → 10+ transition and to derive an effective charge for the i13/2 neutron, which is 0.94±0.04. It is concluded that the quadrupole polarization charge for the i13/2 neutron is about 50% larger than for the h9/2 proton.

I. Bergström

Papers

Effective quadrupole charges in the lead region

Excited nuclear levels in doubly even Xe isotopes populated in (α, 2n) reactions

High spin states and neutron multiplicities after pion capture in181Ta and209Bi

Proton-antiproton annihilations at rest into π0ω, π0η, π0γ, π0π0, and π0η′

E2 CORE POLARIZATION BY NEUTRONS IN THE (i/sub 13/2/)$sup -2$ CONFIGURATION IN $sup 206$Pb.