Chemistry Reference
In-Depth Information
The recent development of the synchrotron radiation facilities (especially the
development of the insertion devices like undulator) has made possible to perform
the nuclear resonance scattering with the synchrotron radiation because of its
extremely high Brilliance (photons/sec/mrad/0.1 % bandwidth) like 10
+17
* 10
+19
for the standard undulator in SPring8 [
26
]. On the other hand, the bandwidth of the
synchrotron X-ray is known to be about a few eV using double single crystal
monochrometor and is extremely large to excite the nuclear levels. Development of
high-resolution monochrometor using 2 nested channel cuts Si crystals reduced the
bandwidth of undulator X-ray to 1.6-3.5 meV with 5 9 10
8
-4 9 10
9
photons/sec/
100 mA, but its bandwidth is still 10
6
times larger bandwidth compared to c photons
in Mössbauer nucleus [
27
]. In order to eliminate the difficulty to observe the photons
by the nuclear resonant scattering with synchrotron radiation, it is now a standard
technique to use the pulsed operation of the synchrotron storage ring and to use the
characteristic time difference in the scattering processes. Thomson scattering occurs
instantaneously, but the emission of photons as a de-excitation of nuclear levels after
the nuclear resonant scattering, roughly speaking, was delayed in time by the lifetime
of the excited state. Schematic illustration for the scattering with the synchrotron
radiation is shown in Fig.
1.9
. Characteristic features of the synchrotron radiation are
as follows; (1) non- radioactive source, (2) high brilliance, (3) white X-ray in prin-
ciple, (2) small beam size with well-collimated beam, (3) linear polarization, and (4)
pulsed operation to form a time domain. In 1974, Ruby proposed to use the syn-
chrotron radiation for the source in Mössbauer spectroscopy [
28
] and now we have
many facilities for the synchrotron radiation at many places in the world [
26
].
Fig. 1.9 Schematic
illustration of the scattering
process with synchrotron
radiation. N nucleus. SR pulse
duration single banch mode
operation of the storage ring
SR
N
SR Pulse
Time
Nuclear
Resonant
Photons
Time
