Theoretical studies of proton capture reactions in A～25 proton-rich nuclei

The direct proton capture and resonance proton capture properties of stellar reactions 22Mg(p,γ)23Al and 26Si(p,γ)27P are studied by employing a mean-field potential obtained from the Skyrme-Hartree-Fock(SHF) model.Calculations with the SHF potential reproduce well the loosely-bound structure of the ground states as well as the widths of the resonant states in these nuclei.With the obtained potential we estimate the reaction rates of direct proton capture and resonance proton capture to nuclei 23Al and 27P....     

Nuclear triaxiality in the A ∼ 160–170 mass region: the story so far

Research in nuclear triaxial deformation has revealed many exciting facts and figures over the last one and a half-decades. Although wobbling motion of nuclei was experimentally discovered at the beginning of the last decade, after almost 25 years of its prediction by Bohr and Mottelson, efforts are still being put to understand this rare nuclear phenomenon in greater detail. The concept of transverse wobbling is one such recent attempt which successfully explains the evolution of experimentally observed wobbling frequency with spin. The population of triaxial strongly deformed (TSD) bands in the A ～160–170 region is favoured for which neutron number (N=92 or 94) is a topic of current debate. Experimental efforts are being put following Bengtsson’s calculations which indicate that the elevated yrast lines for N=92 isotones favour TSD population. In A ～170 mass region, the ambiguity over the real character of certain strongly deformed bands has recently been removed by extensive experimental and theoretical efforts, and the bands have now been firmly established as either enhanced deformed (ED) or superdeformed (SD).     

Microscopic calculation of proton capture reactions in the mass 60–80 region and its astrophysical implications

Microscopic optical potentials obtained by folding the DDM3Y interaction with the densities from the Relativistic Mean-Field approach have been utilized to evaluate S-factors of low-energy (p, γ) reactions in the mass 60–80 region and to compare with experiments. The Lagrangian density FSU Gold has been employed. Astrophysical rates for important proton capture reactions have been calculated to study the behaviour of rapid proton nucleosynthesis for waiting point nuclei with mass less than A = 80.     

Doublet bands in 128La and systematic features of energy separationof doublet bands observed in the A～130 mass region

High spin states of 128La have been studied through the fusion-evaporation reaction 118Sn(14N,4n) 128La at a beam energy of 69 MeV. A positive-parity side band with the same configuration as that of the yrast band has been identified. Moreover, it is noted that the energy separation △E(I) = E(I)side-E(I)yrast of all doublet bands reported in odd-odd nuclei in the A～130 mass region exhibit a staggering pattern systematically, and they stagger up at even-spin and stagger down at odd-spin.     

πg9/2(⊕)vh11/2 doublet bands in A～100 mass region

Using the model with one particle and one hole coupled with a triaxial rotor, the πg(-1)(9/2)(⊕)vh11/2 doublet bands in the A ～ 100 mass region are studied, and compared with the πh11/2(⊕)vh(-1)(11/2) doublet bands.It is found that the calculated results for the configuration of πg(-1)(9/2)(⊕)vh11/2 are very similar the results for a pure h11/2 proton particle and a neutron quasiparticle with λn =ε5. After including the pair correlation, the model describes the candidate chiral doublet bands in 106Rh successfully, which supports the interpretation of chirality geometry.     

First observation of the ν9/2[404] orbital in the A ∼ 100 mass region

A new band, populated by the spontaneous fission of ²⁴⁸Cm and studied by means of prompt γ-ray spectroscopy using the EUROGAM2 array, was observed in ⁹⁹Zr. The 1038.8 keV band head with a half-life T _1/2 = 54(10) ns is interpreted as a K-isomer, corresponding to the 9/2[404] neutron-hole excitation. It is the first observation of this orbital in the mass A ∼ 100 region. The quadrupole moment, Q ₀ = 3.9(3) eb deduced for the new band indicates a large deformation of β = 0.41, which is produced by a specific shape-coexistence mechanism, known in other regions and now found in the A ∼ 100 nuclei. Received: 11 September 2002 / Accepted: 31 October 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: urban@fuw.edu.pl Communicated by D. Schwalm     

原子核同核异能态诱发辐射研究进展

介绍了同核异能态的特点和诱发同核异能态的几种机制,如直接光激发、电子跃迁诱导核激发(NEET)和电子俘获诱导核激发(NEEC)。同核异能态的诱发辐射研究目前在国际上竞争激烈,尤其是对最近提出的NEEC的研究。同时探讨了在我国开展这些研究的可能性。     

Multi-reference calculations of the photodissociation of HSCH3 molecule

This paper performs multi-reference second-order perturbation theory calculations on the ground state and a number of low-lying excited states of HSCH3 molecule, and calculates the vertical excitation energies and low-energy potential-energy curves, based on which the photodissociation channels of HSCH3 at 193,222,248 nm are clarified.     

Radial Functions of Diatomic Lithium Halides X 1Σ+ From Vibration-Rotational Spectra

The radial functions for potential energy and adiabatic and nonadiabatic effects in the forms of polynomials with coefficients c_j, h_j ^Li, h_j ^X, g_j ^Li and g_j ^X of the reduced variable for internuclear distance z=2.(R-R_e)/(R+R_e) to various non-negative powers have been determined for the family of diatomic molecules of the lithium halides, LiF, LiCl, LiBr and LiI, with the corresponding results of LiH included for purposes of comparison. Trends are evident in the coefficients of lower order, but those of higher order are susceptible not only to the influence of the extent and quality of the data but also to the truncation of the power series in the representations. The various radial functions are valid with the specified ranges of internuclear distance depending on the maximum extent of vibrational excitation of the spectra.     

原子核同核异能态诱发辐射研究进展

介绍了同核异能态的特点和诱发同核异能态的几种机制,如直接光激发、电子跃迁诱导核激发(NEET)和电子俘获诱导核激发(NEEC)。同核异能态的诱发辐射研究目前在国际上竞争激烈,尤其是对最近提出的NEEC的研究。同时探讨了在我国开展这些研究的可能性。     

Alpha radioactivity for proton-rich even Pb isotopes

Half-lives for alpha radioactivity from proton-rich even Pb isotopes in the range A = 182–202 have been calculated using the unified fission-like approach. The geometrical shape of the potential barrier is parametrized in terms of a highly versatile, asymmetric and analytically solvable form of potential based on Ginnochio’s potential. Good agreement with the experimental data has been obtained with the variation of just one parameter. Half-lives of three unknown alpha emitters in the neutron-deficient Pb chain (¹⁹⁸Pb, ²⁰⁰Pb and ²⁰⁴Pb) have been predicted. The exact expression for the transmission coefficient has been compared with those obtained from WKB approximation method for symmetric Eckart potential.      

原子数据库在研究同核异能态诱发辐射中的应用

如何人为地诱发同核异能态辐射,从而利用储存在其中的巨大能量,是个备受关注的交叉学科课题。利用原子物理过程进行触发是目前较为可行的方案,原子物理参数将在里面起到关键作用。介绍了一套高效率的原子数据库,目前该数据库可对原子序数小于96的元素所有电离度离子的能级结构信息进行快速扫描,从而筛选出一些可能通过原子过程触发的同核异能态体系。通过在197Au元素电子跃迁诱导核激发过程和178Hf元素电子俘获诱导核激发过程中的应用,展示了该数据库对寻找合适同核异能态体系的作用。     

The surfaces of compact systems: from nuclei to stars

While providing information from worlds separated by five-to-six orders of magnitude in dimensions and in energy, the pairing properties (electrical resistance and viscosity), the electromagnetic response (spectrum of colours), the resilience to stress (elasticity), the ability to deform (plasticity), etc., associated with clusters of atoms and with atomic nuclei have surprisingly similar properties, once the proper scalings are done, and demonstrate the many analogies that can be drawn between different finite many-body systems. These analogies can be further extended to cosmic and to customer tailored nanometre materials. Femtometre materials, like the inner crust of a neutron star (pulsar), are made out of the same protons and neutrons which make infinite nuclear matter. However in pulsars, protons and neutrons are arranged in the form of finite nuclei immersed in a sea of free neutrons. This is the reason why these celestial objects rotate, conduct heat, emit neutrinos, etc., very differently from infinite nuclear matter. In fact, these phenomena reflect the properties of the corresponding atomic nuclei which form the pulsar. Among these properties, those associated with the nuclear surface are most important. Nanostructured materials are made out of atoms as their more common forms, but the atoms are arranged in nanometre or sub-nanometre-size clusters, which become the constituent grains, or building blocks, of new materials like, e.g., C₆₀ fullerene. Because these tiny grains respond to light, mechanical stress and electricity quite differently from micron- or millimetre-sized grains, nanostructured materials display an array of novel attributes. At the basis of the new phenomena we find again the surface of the building blocks used to produce the new materials. A proper understanding of the interweaving of the single-particle motion with the static and dynamic deformations of the surface of finite many-body systems is likely to provide the key to open a whole new world of interdisciplinary research in such disparate fields as isolated atomic nuclei and clusters, new materials and compact stellar objects. The concepts and the experimental evidence needed to tool this key will be reviewed. Special emphasis will be set on the open questions still remaining to be answered to reach this goal.     

原子数据库在研究同核异能态诱发辐射中的应用

 如何人为地诱发同核异能态辐射,从而利用储存在其中的巨大能量,是个备受关注的交叉学科课题。利用原子物理过程进行触发是目前较为可行的方案,原子物理参数将在里面起到关键作用。介绍了一套高效率的原子数据库,目前该数据库可对原子序数小于96的元素所有电离度离子的能级结构信息进行快速扫描,从而筛选出一些可能通过原子过程触发的同核异能态体系。通过在¹⁹⁷Au元素电子跃迁诱导核激发过程和¹⁷⁸Hf元素电子俘获诱导核激发过程中的应用,展示了该数据库对寻找合适同核异能态体系的作用。     

Ultraslow phonon-assisted collapse of tubular image states

We predict ultraslow collapse of “tubular image states” (TIS) on material surfaces. TIS are bound Rydberg-like electronic states formed at large distances (∼30 nm) from the surfaces of suspended circularly-symmetric nanowires, such as metallic C nanotubes. The states are formed in potential wells, resulting from a combination of the TIS-electron attraction to image charges in the nanotube and its centrifugal repulsion, caused by spinning around the tube. We demonstrate that TIS can collapse on the tube surface by passing their angular momentum l to circularly polarized flexural phonons excited in the tube. Our analysis shows that for highly detached TIS with l ? 6 the relaxation lifetimes are of the order of 10 ns-1 μs, while for l < 6 these lifetimes are reduced by several orders of magnitude.     

Dynamical phenomena including many body effects at metal surfaces

In this contribution, we give a brief survey of some elementary many body processes observable at surfaces. We begin the survey by discussing how the electron ground state would behave and look like in real space at surfaces. Next, we discuss how these electrons behave when they are perturbed by external fields characterized by ultrashort time scales. We follow this with a discussion of how the dynamics of electrons would then affect the motion of adsorbates on surfaces. Finally, we cite some possible technological applications utilizing this knowledge. We also discuss possible trends or directions of scientific research in this century.