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

Evidence for two-particle core polarization in the isomeric 29/2 + and 21/2 - states of theπ ( {h_{{9 2}}^2 } )_{8^ + } i_{1 {3 2}} vleft( {j^{ - 2} } )_{0^ + } andπ ( {h_{{9 2}}^3 } )vleft( {j^{ - 2} } )_{0^ + } configurations in 209 At

High-spin states in 210Po (16+, 14-, 13-) and 211At (39/2-, 33/2+, 31/2+) have been studied by measurements of delayed gamma rays and conversion electrons produced in 208Pb(α, 2n)- and 209Bi(α, 2n)-reactions. In conventional time differential perturbed angular distribution (TDPAD) experiments the following half-lives and g-factors were found: T1/2(16+) = 265(10) ns; T1/2(13-) = 51(2) ns; g(16+) = 0.615(5); g(13-) = 0.526(13); g(39/2-) = 0.690(7). The 16+ state in 210Po was found to decay by a 685 keV E3 transition with the B(E3) value 19(1) W.u., and a 280.3 keV M2 transition with a B(M2) value of 0.12(1) W.u. The electromagnetic properties and the calculated level energies require the following configurations: Using the magnetic moments and transition probabilities of the relevant levels the mixing amplitudes are estimated and it is found that relatively small admixtures are important for the understanding of the experimentally determined electromagnetic properties.

On the Electromagnetic Properties of Core-Excited High-Spin States in 210Po and 211At

Using the pulsed alpha-beam of the 225 cm cyclotron, we have found a 93 nanosecond level in 210Po at 4 372.0 keV, which we interpret as a state arising from two protons in the (h9/2)82 state, coupled to the first 5- state in 208Pb.

Evidence for High-spin Core-excited States in 210Po

The inclusive η-momentum spectrum from {Mathematical expression} annihilations at rest in liquid hydrogen was measured at LEAR. Branching ratios were obtained for {Mathematical expression}, and ηη( ...

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Experimental study of the inclusiveη-spectrum fromp\(\bar p\) annihilations at rest in liquid hydrogen

The reactions 205Tl(α, 2n)207Bi and 208Pb(d, 3n)207Bi were studied using α-particles in the energy range 30-43 MeV and deuterons at the energy 25 MeV. In-beam prompt and delayed γ-ray and conversion electron spectroscopy investigations reveal an isomeric 29/2- state at 3887.7 keV with the half-life 13 ± 1 ns, which is suggested to have the configuration πh9/2 vi13/2-2. This isomeric state decays by a cascade of three γ-rays (386.8, E1; 899.3, M1; 499.7, E2) to states with Jπ = 27/2+, 25/2+, and to the previously known 21/2+ isomeric state with the configuration πh9/2 vp1/2-1 i13/2-1. In this state the probability of the spatial coincidence of all three valence nucleons is large and it may therefore be affected by a short-range three-body interaction. By comparing the experimental and calculated energies, assuming only two-body forces, it is found that the three-body energy is less than 10 keV in the 27/2+ state. This upper limit is not much larger than the expected effect, which is estimated to be of the order of 2 keV by comparing with the three-body energy in 3H.

I. Bergström

Papers

Evidence for two-particle core polarization in the isomeric 29/2 + and 21/2 - states of theπ ( {h_{{9 2}}^2 } )_{8^ + } i_{1 {3 2}} vleft( {j^{ - 2} } )_{0^ + } andπ ( {h_{{9 2}}^3 } )vleft( {j^{ - 2} } )_{0^ + } configurations in 209 At

On the Electromagnetic Properties of Core-Excited High-Spin States in 210Po and 211At

Evidence for High-spin Core-excited States in 210Po

Experimental study of the inclusiveη-spectrum fromp\(\bar p\) annihilations at rest in liquid hydrogen

High-Spin States in 207Bi and the Question of Three-Particle Interactions