Extreme deformation: First results from the new Radioactive Ion Beam Factory in Japan
The observation of extreme deformation of the exotic nucleus 32Ne
marks the first major scientific discovery at the newly constructed
Radioactive Ion Beam Factory in Japan, a new-generation facility whose
construction started over 10 years ago. Atomic nuclei can assume a
non-spherical shape, which is one of their most fascinating properties
and directly intertwined with the notion of "magic" neutron and proton
numbers. A nucleus composed of a magic number of protons or neutrons
is particularly stable, spherical and difficult to excite. In this
paper, we report on the first strong evidence of very large
deformation of the isotope 32Ne, which is extremely difficult to
produce and investigate in the laboratory, owing to its very
unbalanced ratio of 22 neutrons to only 10 protons, almost at the
limit of nuclear stability. Shooting a beam of 32Ne nuclei with a
velocity of 60% of the speed of light onto a Carbon target, we were
able to observe a single gamma-ray transition with an unexpectedly low
energy, indicative of a very large ground state deformation, despite
its vicinity the magic neutron number N=20. This is further evidence
of a softening of nuclei and an erosion of the usual magic numbers
toward the drip-lines.
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LB12491B
Sorting electrons by spin: Some surface alloys do the work
At metal surfaces, some electrons behave like a two-dimensional gas:
They move freely along the surface but are trapped in perpendicular
direction. Since electrons possess a spin which can be either `up' (red
spheres in the figure) or `down' (green spheres), the confinement
produces a specific arrangement of the electrons' velocities: The faster
electrons moving, say, to the right are spin-up whereas their slower
colleagues are spin-down (left panel). If they travel in opposite
direction, their spins become reversed. The velocity difference, named
Rashba effect, is particularly large in surface alloys made of heavy
elements (e.g. Bi) on a noble metal surface, for example Ag.
For the surface alloy Bi/Cu(111), we have shown by photoemission
experiments and first-principles calculations that some of the slow and
the fast electrons which move in the same direction can have identical
spins (right panel). Consequently, more spin-up electrons travel to the
right as to the left and vice versa. Spin-up and -down electrons would
gather at opposite sides of a nano-device, turning its edges magnetic.
This `sorting by spin' makes metallic surface alloys promising materials
for future spin-electronics applications.
