| X-ray Absorption
Spectroscopy |
 X-ray
absorption spectroscopy (XAS) takes advantage of the continuous
emission spectrum of synchrotron radiation, in which the incident
photon energy is scanned by using a monochromator and the absorption
coefficient of the sample is recorded against the energy. In general,
one spectrum can be roughly divided into three regions, namely,
pre-edge, near-edge (XANES), and post-edge (EXAFS) regions. The
XANES can reflect the electronic properties of the absorbing atom
(such as the oxidation state and d-orbital occupancy) and can be
utilized to distinguish different site symmetry. On the other hand,
the EXAFS provides the information of local atomic structure around
the absorbing atom, including the type and the number of atoms in
specific coordination shell, the interatomic distance, and the structural
disorder. The samples are not required to have a structure of long-range
order so that either crystallite or amorphous solid and even liquid
or gas all can be measured. If the sample consists of many elements,
each individual element can be measured by tuning the photon energy
to the absorption edge of the corresponding element. For a biological
sample system, X-ray absorption spectroscopy has been widely employed
to probe the electronic structure (particularly oxidation state)
and atomic structure (formation and breaking of chemical bonding)
of the metal center during the course of biochemical reaction.
Introduction of XAS
Beamline
|
Energy Range
(keV) |
Beam Size
(mm) |
Flux (p/s) |
Detector |
| BL17C1 |
5-14 |
6(H)x2(V) |
5.0x1010 |
13-Element Ge SSD, Lytle Detector,
Ion Chambers |
|
|
