1 Historical Developments and Future Perspectives …
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domain interferometry (TDI) [69] and in the energy domain with Rayleigh scattering with Mössbauer radiation (RSMR) [70, 71].
The TDI setup includes the sample under investigation and two resonance
absorbers. The first one is placed in the path of the incident radiation upstream of
the sample and the second one downstream of the sample in the path of the scattered
radiation at the defined momentum transfer under investigation.
In the default scheme [69], these are single-line absorbers. One of those is at
rest, the other one is driven by a MB transducer with constant velocity, defining the
difference in the energies of the two nuclear resonance transitions. A partial probability of nuclear forward scattering of each photon by the upstream and downstream
absorbers gives the probe and the reference wave, respectively.
In absence of slow dynamics, nuclear forward scattering from both samples proceeds elastically, and an interference of the probe and reference waves displays quantum beats, defined by the difference in the resonance energies of the two absorbers.
Under relaxation conditions, nuclear forward scattering of the probe wave acquires
with time a phase shift, which damps the beats. The envelope of the fading contrast
of the quantum beats provides the momentum-transfer dependent auto-correlation
function of the density fluctuations (intermediate scattering function) [69].
For the RSMR set-up a radioactive source or a nuclear monochromator, the SMS,
prepares a high-resolution γ -ray beam and after the sample a resonance detector
analyzes the scattered radiaton at the defined momentum transfer under investigation. In absence of dynamics the MB spectrum resembles the source characteristics
whereas in case of dynamics the line width will broaden according to the dynamics.
A detailed description of RSMR with SR will be given elsewhere in this book by
Seto et al. [60].
1.3.6 Inelastic Scattering
1.3.6.1 Nuclear Inelastic Scattering
Nuclear inelastic scattering [72] measures the (partial) phonon density of states
(DOS) of the Mössbauer element in the sample [72–74]. The principle set-up is
shown in Fig. 1.7 NIS.
The synchrotron radiation is monochromatized by a high resolution monochromator (HRM) with (sub-) meV energy resolution. At resonance the x-ray pulse creates a
coherent collective nuclear state as in NFS, which decays either in forward direction
or incoherently, due to internal conversion, spin flop etc., in the entire solid angle of
4π. This feature gives a simple and effective method at hand to measure the instrumental function (detector NFS) in parallel with the inelastic spectrum (detector NIS).
While scanning the HRM the nuclear resonance can be excited when at the same time
a phonon is created or annihilated. In NIS this is a purely incoherent process with a
perfect averaging over the momentum q. The successive nuclear decay proceeds as
23
domain interferometry (TDI) [69] and in the energy domain with Rayleigh scattering with Mössbauer radiation (RSMR) [70, 71].
The TDI setup includes the sample under investigation and two resonance
absorbers. The first one is placed in the path of the incident radiation upstream of
the sample and the second one downstream of the sample in the path of the scattered
radiation at the defined momentum transfer under investigation.
In the default scheme [69], these are single-line absorbers. One of those is at
rest, the other one is driven by a MB transducer with constant velocity, defining the
difference in the energies of the two nuclear resonance transitions. A partial probability of nuclear forward scattering of each photon by the upstream and downstream
absorbers gives the probe and the reference wave, respectively.
In absence of slow dynamics, nuclear forward scattering from both samples proceeds elastically, and an interference of the probe and reference waves displays quantum beats, defined by the difference in the resonance energies of the two absorbers.
Under relaxation conditions, nuclear forward scattering of the probe wave acquires
with time a phase shift, which damps the beats. The envelope of the fading contrast
of the quantum beats provides the momentum-transfer dependent auto-correlation
function of the density fluctuations (intermediate scattering function) [69].
For the RSMR set-up a radioactive source or a nuclear monochromator, the SMS,
prepares a high-resolution γ -ray beam and after the sample a resonance detector
analyzes the scattered radiaton at the defined momentum transfer under investigation. In absence of dynamics the MB spectrum resembles the source characteristics
whereas in case of dynamics the line width will broaden according to the dynamics.
A detailed description of RSMR with SR will be given elsewhere in this book by
Seto et al. [60].
1.3.6 Inelastic Scattering
1.3.6.1 Nuclear Inelastic Scattering
Nuclear inelastic scattering [72] measures the (partial) phonon density of states
(DOS) of the Mössbauer element in the sample [72–74]. The principle set-up is
shown in Fig. 1.7 NIS.
The synchrotron radiation is monochromatized by a high resolution monochromator (HRM) with (sub-) meV energy resolution. At resonance the x-ray pulse creates a
coherent collective nuclear state as in NFS, which decays either in forward direction
or incoherently, due to internal conversion, spin flop etc., in the entire solid angle of
4π. This feature gives a simple and effective method at hand to measure the instrumental function (detector NFS) in parallel with the inelastic spectrum (detector NIS).
While scanning the HRM the nuclear resonance can be excited when at the same time
a phonon is created or annihilated. In NIS this is a purely incoherent process with a
perfect averaging over the momentum q. The successive nuclear decay proceeds as