Buckyball monolayer
electronic structure
by Art Robinson
The 1980s witnessed the discovery of
fullerenes, whose novel properties have been intensively studied
by experiment and theory but remain incompletely understood.
Among the fullerenes, for example, the solid formed from C60
molecules exhibits superconductivity at the relatively high
temperature of about 40 K when doped with alkali metal atoms
(only the high-Tc cuprate superconductors have higher transition
temperatures). A Berkeley/Stanford/Italian collaboration working
at the ALS has now reported angle-resolved photoemission measurements
of C60 (buckyball) monolayers doped with potassium.
They were able to detect, for the first time, both the band
structure and a Fermi surface, two classical electronic structure
features that surprisingly survive in the presence of the
strong interactions in this material. Full
story.
Publication about this research: W.L. Yang,
V. Brouet, X.J. Zhou, H.J. Choi, S.G. Louie,
M.L. Cohen, S.A. Kellar, P.V. Bogdanov, A. Lanzara,
A. Goldoni, F. Parmigiani, Z. Hussain, and
Z.-X. Shen, "Band structure and Fermi surface of
electron-doped C60 monolayers," Science 300,
303 (2003).
Contacts: Wanli Yang, WLYang@lbl.gov;
Z.-X. Shen, zxshen@stanford.edu
Daniel Chemla
recovering from surgery
On December 15, ALS Director Daniel
Chemla was admitted to the UC San Francisco hospital for surgery
to remove an arteriovenous malformation in his cerebellum.
The best prognosis at the time was that he would be in intensive
care for four to five days and then be home for the holidays.
However, because of the need for a second operation and other
complications, he was not released from intensive care until
January 6. On January 20, he was transferred to
a rehab center in Berkeley, where he is slowly regaining his
strength. There is a possibility that he will be home by the
end of February. While we all look forward to his return to
the ALS, it will not be for some time. In the meantime, his
responsibilities are being shared by his three deputies, Ben
Feinberg, Jim Krupnick, and Neville Smith, who are moving
forward in implementing the agenda that Daniel has very clearly
laid out for 2004.
Contact: Neville Smith, NVSmith@lbl.gov
ALS x-ray microscopes
see up close
One of the promises of high brightness is the ability
to do spatially resolved experiments (imaging, spectroscopy,
and scattering). Two of the premier instruments in the world
for these purposes are at the ALS: the veteran full-field
transmission x-ray microscope (XM-1) on bend-magnet Beamline
6.1.2 and the new scanning transmission x-ray microscope (STXM)
on undulator Beamline 11.0.2. Both instruments are based on
Fresnel zone-plate lenses made at Berkeley Lab's Center for
X-Ray Optics (CXRO), and they are regularly achieving spatial
resolution better than 30 nm with the newest zone plates.
 CXRO
was featured in the Optical Society of America's "Optics
in 2003" highlights for the clear demonstration of 20-nm
spatial resolution, obtained with the soft x-ray microscope
XM-1 at ALS Beamline 6.1.2. The measured resolution is the
highest achieved with photon-based imaging optics." The
highlight appeared in the December
2003 issue of Optics & Photonics News, published by
the Optical Society of America. The microscope, designed and
built by CXRO, operates at photon energies from 300 eV to
1800 eV (or wavelengths from 0.7 nm to 4 nm). It provides
large elemental and magnetic sensitivity, penetration depths
up to 10 micrometers, and in-situ imaging at cryogenic and
elevated temperatures, in applied magnetic fields, and with
applied electric currents. The microscope has a throughput
of as many as 1,000 images a day. Research areas studied with
the microscope include biology, environmental science, magnetism
and electromigration. Tomographic reconstructions from images
at multiple angles gives a three-dimensional imaging capability.
The original STXM on Beamline 7.0.1 at
the ALS was always highly regarded for its potential. However,
Beamline 7.0.1 is a multipurpose beamline and was not optimized
for imaging, thus compromising the STXM's performance. Recently,
a significantly upgraded version of the STXM was moved to
a branch of the new Molecular Environmental Science (MES)
Beamline 11.0.2 that was designed to match STXM operational
requirements. The combination of an optimized beamline, improved
scanning stability and placement accuracy, and an advanced
zone plate from CXRO have enabled the STXM to realize the
promised potential. Current Beamline 11.0.2 STXM parameters
include a photon-energy range from 150 eV to 2000 eV, a flux
up to 109 photons/s at a resolving power of 3000, a theoretical
spot size of 30 nm, and a spatial resolution that has not
yet been precisely characterized but is sufficient to see
details in 25-nm patterns. In addition, an elliptically polarizing
undulator (EPU) permits linear and circular dichroism studies
with spatial resolution well below the 100-nm scale. A number
of experiments on magnetic, environmental, and biological
samples have been performed. There is a similar instrument
(the polymer STXM) on bend-magnet Beamline 5.3.2.
Contacts: Weilun Chao, WLChao@lbl.gov;
Tolek Tyliszczak, tolek@lbl.gov
UEC Corner: Notes
from the Users'
Executive Committee
by Dennis Lindle
The first UEC meeting of 2004 is scheduled for March 2
in Room 6-2202 at 9:00 a.m. Topics will include updates on
planned ALS upgrades and the proposed Users' Services Building,
discussions of ALS strategic planning, organization of the
2004 ALS Users' Meeting, as well as continuing discussion
of issues directly impacting users' interactions with the
ALS and Berkeley Lab, such as housing and parking. As always,
nearly all of the meeting will be open to anyone from the
user community or the ALS—please join us if you can.
If you have any suggestions or comments for the UEC or the
ALS and cannot be there in person, please feel free to contact
me or any of the other members of the UEC (please refer to
the ALS web site). We would be especially interested to hear
your thoughts about planned upgrades to the ALS (e.g., top-off
mode) and to receive suggestions for this year's Users' Meeting.
(Contact: Dennis Lindle, lindle@unlv.nevada.edu)
Ultrafast x-ray
science workshop
coming in April
 A
workshop on ultrafast x-ray science will be held from April 28
to May 1, 2004, in San Diego, California. The goals of
the workshop are to identify scientific highlights and directions
for the use of x-ray techniques, to promote the cross-fertilization
of ideas at the common forefront of the laser- and accelerator-based
communities, and to define the source characteristics and
ancillary equipment required for productive user facilities
for ultrafast x-ray science. Students and those new to the
field are specifically urged to attend to learn about this
exciting field, which also includes breathtaking advances
in the attosecond time domain. The registration deadline is
March 22, 2004. For further information, go to the workshop
Web site.
Contact: Steve Leone, SRLeone@lbl.gov;
John Corlett, JNCorlett@lbl.gov
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