On the yrast two proton-two neutron hole states in208Po

High-spin levels in²⁰⁸Po, populated in the²⁰⁸Pb(α,4n)-reaction, were studied usingα-particles in the energy region 41–51 MeV. The energies of levels above the 6⁺ level have an uncertainty of about 10 keV due to the fact that the 8⁺→6⁺ transition has not been observed so far, but this transition has previously been established to be converted neither in theK-shell nor in theL-shells. It was found that the yrast cascade ofγ-rays from a 19⁺ level at 5896+ε keV feeds levels of lower spin which all can be explained as originating from two proton-two neutron hole configurations. In the higher part of the cascade it is mainly the neutron holes which change their configuration, while the lower part of the cascade is dominated by changes in the proton configuration. The yrast levels in the angular momentum regionJ=8–19 vary practically linearly with energy in the region 1.5–6 MeV. No isomeric traps were found above the 11^? level at 2699+ε keV.     

Double-octupole states in 208Pb

The states of 208Pb are calculated in a 24 orbit model space which includes all excitations up to two particles and two holes beyond the closed shell. All of the known low-lying states are reproduced by this model. The observed distributions of electromagnetic excitation strength from the ground state to low-lying excited states are well described by the model. The double-octupole excitation strength is calculated and found to be concentrated in 0+, 2+, and 4+ states around 5.2 MeV, but it is fragmented over many 6+ states, in agreement with recent experiments.     

High-spin states in 208Pb

High-spin states in ²⁰⁸Pb have been studied by γ-ray-spectroscopy methods in deep inelastic reactions induced by beams of ²⁰⁸Pb, ¹³⁶Xe and ⁷⁶Ge beams on a thick ²⁰⁸Pb target. The 11⁺ ₂ state and new γ-transitions between the one-particle one-hole states of highest spin have been found and electromagnetic matrix elements verified. High-spin states of two-particle two-hole structure have been detected for the first time. The results are compared to shell model calculations with realistic interactions in the complete Kuo-Herling space. Received: 31 October 2000 / Accepted: 26 March 2001     

The role of two particle-two hole excitations in the spin-isospin nuclear response

We investigate the role of the 2p-2h states in the spin-isospin nuclear response function. This is done in the frame of a microscopic approach which includes the meson exchange currents and the nucleon-nucleon correlation. We first test our theory on the transverse response in the inclusive deep inclastic electron scattering, where we achieve a satisfactory agreement with the data for values of the momentum transfer ranging from 1 to 2 fm^?1. We next explore the p-wave pion-nucleus absorptive optical potential. We find that a strong (～3) Lorentz-Lorenz-Ericson-Ericson quenching factor is needed to reproduce in our framework the phenomenological optical potential deduced from π-mesic atom data. We also examine the real photon absorption cross section accounting rather satisfactorily for its behaviour, in particular for the Pauli blocking at small frequencies. Finally, we elucidate the conditions for the existence of a connection between the magnetic photon absorption and the p-wave pion absorption in nuclei.     

Particle octupole-vibration coupling near 208Pb

High-spin states in ²⁰²Pb and ²⁰³Pb have been investigated by in-beam γ-ray spectroscopy following the reaction ¹⁹⁸Pt(⁹Be,xn). A search for magnetic rotational bands in these isotopes confirmed one of the two bands previously assigned to ²⁰²Pb and revealed a new band in this isotope. No evidence for magnetic rotation has been found in ²⁰³Pb. Received: 24 July 2000 / Accepted: 28 September 2000     

Proton decay of the isobaric analogs of the ground states of207Pb and208Pb

The proton decays \(\tilde p\) of isobaric analog states of^{207, 208}Pb in the reactions^{207, 208}Pb(p, n) have been studied using a neutron-proton coincidence technique. The width anomaly observed in (p, n) [4] and (p, n \(\tilde p\) ) singles spectra [11] is resolved in the coincident spectra.     

The distribution of205Tl proton hole states and estimation of the root mean square radii of206Pb and208Pb from their charge distributions

The fragmentations of the 3s _1/2, 2d _3/2, 2d _5/2 and 1.h _11/2 proton states were deduced using the hole-core coupling model calculation and compared with recent²⁰⁶Pb ( \(\vec d\) ,³He) reaction data. The energies of the proton fragments carrying the main shell-model strengths were used to deduce the radial wave functions of²⁰⁵T1 and²⁰⁷Tl that give rise to charge distributions of these nuclei. From their respective charge distributions, root mean square radii of²⁰⁶Pb and²⁰⁸Pb were extracted.     

The role of the tensor force for high-spin states of unnatural parity in 208Pb

The influence of the residual particle-hole tensor force on the wavefunctions of the high-spin states of unnatural parity in ²⁰⁸Pb is investigated. The form factors for the electroexcitation of such states have been calculated within the formalism of the random-phase approximation with and without the consideration of the meson exchange currents in the nuclear electromagnetic current. Special attention is devoted to the 12⁻ states which appear to be very good places to look for the effects of interest.     

Spectrum of the high spin neutron hole states of205Pb

The high resolution (³He,α) reaction on²⁰⁶Pb shows the distribution of the 2f _7/2, 1h _9/2 and 1i _{1 3/2} neutron states of²⁰⁵Pb within the 6 MeV excitation energy of²⁰⁵Pb. The spectrum of these three-hole states is obtained within the hole-core vibrational coupling scheme. The shell model energies of the neutron hole states arising from the core-polarization effect are compared with the Bansal-French energy weighted sum rule. The possible implication of the present neutron hole energies has been discussed in the light of the deduced shell model wave functions of the collective states of²⁰⁶Pb.     

Excitation energies of particle-hole states in 208Pb and the surface delta interaction

The schematic shell model without residual interaction (SSM) assumes the same excitation energy for all spins in each particle-hole configuration multiplet. In ²⁰⁸Pb, more than forty states are known to contain almost the full strength of a single particle-hole configuration. The experimental excitation energy for a state with a certain spin differs from the energy predicted by the SSM by ?0.2 to +0.6 MeV. The multiplet splitting is calculated with the surface delta interaction; it corresponds to the diagonal matrix element of the residual interaction in the SSM. For states containing more than 90% strength of a certain configuration and for the centroid of several completely observed configurations, the calculated multiplet splitting often approximates the experimental excitation energy within 30 keV. The strong mixing within some pairs of states containing the full strengths of two configurations is explained.     

Mode coupling theory for the critical dynamics of dipolar ferromagnets

The critical dynamics of ferromagnets has been studied by various experimental methods sampling different regions in wave vector space. Nevertheless there seemed to be a list of contradictions between these experiments. Within a mode coupling theory including both short range exchange and long range dipolar interaction we are able to resolve the seemingly contradictory situation.     

Neutron particle-hole electric dipole states in 206, 207, 208Pb

Inelastic proton scattering on ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb through isobaric analog resonances has been used to study neutron particle-hole excitations with large ground-state γ-branches in these Pb isotopes. Relative (p, p′) cross sections at 90° are extracted for structures selectively excited on the $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{,}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{and d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{?}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ resonances. Interpretation of excitations is ²⁰⁶Pb and ²⁰⁷ Pb in terms of coupling to states in ²⁰⁸Pb is discussed. Branching ratios for 1^?states in ²⁰⁸Pb at 4.84, 5.29, 5.94 and 6.31 MeV and the $\text{1}\text{2}{}^{\mathrm{+}}$ state in ²⁰⁷Pb at 4.63 MeV are deduced.     

Excited states populated via nucleon transfer in the reaction32S +208Pb

The population strengths of excited states in nuclei produced via transfer reactions in the 185 MeV³²S +²⁰⁸Pb reaction have been investigated by heavy-ion- coincidence techniques. The cross sections extracted from the spectra, have been analyzed in the framework of the Complex WKB approximation theory.     

Republication of: Black hole equilibrium states Part II. General theory of stationary black hole states

This is a reprinting of Part 2 of Brandon Carter’s lectures given at the 1972 Les Houches school on black holes, first published in a book of proceedings of that school in 1973, in which the author presents a general theory of stationary black holes. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. Several errors of the original text were corrected for this reprinting by the author. The reprinted article is accompanied by an editorial note written by Marek Abramowicz.     

Nucleon transfer reactions to rotational states induced by206, 208Pb projectiles

In a systematic study of nucleon transfer reactions accompanied by Coulomb excitation we have bombarded¹⁵²Sm,¹⁶⁰Gd and²³²Th with^{206, 208}pb beams at incident energies close to the Coulomb barrier. Particle-gamma coincidence techniques were used to identify excited states of reaction products populated through inelastic scattering and in nucleon transfer reactions. One-neutron stripping and pick-up reactions on¹⁵²Sm were observed leading to known states of the rotation alignedi _13/2-bands in¹⁵³Sm and¹⁵¹Sm. In the¹⁶⁰Gd+^{206, 208}Pb systems no significant population of low lying states of product nuclei was found in the nucleon-transfer channels. Large cross sections were observed for one- and two-neutron pick-up from²³²Th at an incident energy of 6.4 MeV/u. Around the grazing angle they are of the same order of magnitude as the cross section measured for inelastic scattering. The results are analyzed in the framework of semiclassical models.     

Fully self-consistent description of high spin magnetic states in 208Pb

Magnetic transverse form factors of 12^? and 14^? states in ²⁰⁸Pb are calculated in a fully self-consistent manner utilizing the effective density dependent interaction D1. Reduction of the strength due to the RPA polarization and the ground state correlations is observed and found to be independent of the momentum transfer. Nuclear structure implications particular to two close lying 12^? states are discussed.     

Time-dependent quantum description of few-nucleon transfers upon nuclear reactions 40Ca + 96Zr, 40Ca + 208Pb, and 90Zr + 208Pb

The time-dependent Schrödinger equation is solved numerically using the difference approach for outer nucleons of the spherical nuclei ⁴⁰Ca, ⁹⁰Zr, and ²⁰⁸Pb upon their grazing collisions. The neutron and proton transfer probabilities are determined for energies near the Coulomb barrier as functions of the minimum internuclear distance and quantum numbers of initial nucleon states.