ISSN:0031-9228    

DOI:10.1063/1.2809084

出版商:AIP    

年代:1993

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2809085

出版商:AIP    

年代:1993

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2809086

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Everyone who has completed an elementary quantum mechanics course has seen plots of solutions of the Schro¨dinger equation for the archetypal “particle in a box.” Now IBM researchers have used scanning tunneling microscopy to image the rippled density of states of electrons inside a “corral” built with a few dozen carefully positioned iron atoms on a copper surface. (See the cover of this issue.) The spectacular results closely match theoretical models of the system.

ISSN:0031-9228    

DOI:10.1063/1.2809087

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Unlike babies, which are usually named at birth, a number of heavy elements have remained anonymous even though some are nearly 30 years old. These nameless orphans have been the objects of bitter custody battles: Three major research groups—located at the University of California at Berkeley, the Joint Institute for Nuclear Research in Dubna, Russia, and the Laboratory for Heavy Ion Research (GSI) in Darmstadt, Germany—have competed intensely for years to produce the heavy elements and have filed conflicting claims for discovery. But given the difficult nature of the experiments on such short‐lived isotopes, it hasn't always been clear which group has really produced a given element

ISSN:0031-9228    

DOI:10.1063/1.2809088

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

There's more to research on heavy elements than simply producing them. Recent experiments continue to explore their properties. In a welcome collaborative effort, researchers from the Joint Institute for Nuclear Research in Dubna, Russia, and from the Lawrence Livermore National Laboratory announced at the Actinides ‘93 Conference in Santa Fe, New Mexico, in September that they had produced an isotope of element 106 that emits an alpha particle with a particularly low energy within a decay time between 10 and 30 sec. That's long compared with the lifetimes of microseconds to milliseconds that are more typical of the elements at the upper end of the periodic table.

ISSN:0031-9228    

DOI:10.1063/1.2809089

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Atoms wandering on surfaces lead complex lives. For example, they face many restrictions on their freedom to move. High walls sometimes leave only one road open, and that road may have checkpoints. Such walls and checkpoints are a consequence of the crystal structure of the surface and the interaction between the surface atoms and the wandering atom. The crystal structure in turn is controlled by the nature of the bonding—metallic, covalent, ionic—between atoms in the crystal.

ISSN:0031-9228    

DOI:10.1063/1.881367

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A deep sense of unease permeates the physical sciences. We are in a time of great change: The end of the cold war has ushered in an era of shrinking budgets, painful restructuring and changing objectives. At the same time, the underlying assumptions of physics research have shifted. Traditionally, physics has been highly reductionist, analyzing nature in terms of smaller and smaller building blocks and revealing underlying, unifying fundamental laws. In the past this grand vision has bound the subdisciplines together. Now, however, the reductionist approach that has been the hallmark of theoretical physics in the 20th century is being superseded by the investigation of emergent phenomena, the study of the properties of complexes whose “elementary” constituents and their interactions are known. Physics, it could be said, is becoming like chemistry.

ISSN:0031-9228    

DOI:10.1063/1.881368

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

In July of this year, at the College of William and Mary in Williamsburg, Virginia, the United States hosted for the first time the International Physics Olympiad, an annual competition open to pre‐college students from all over the world. (See the article by Barbara Goss Levi inPHYSICS TODAY, September, page 40, and the accompanying box by Arthur Eisenkraft.) The olympiad is a major cultural and social event, lasting a full week. The examination itself occupies only two half‐days of that time; it is, however, theraison d'êtreunderlying the whole occasion, and the creation of an appropriate test is a considerable challenge, as well as a very interesting experience.

ISSN:0031-9228    

DOI:10.1063/1.881369

出版商:AIP    

年代:1993

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2809090

出版商:AIP    

年代:1993

数据来源: AIP