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M. Seto et al.
method is called as RSMR [111]. However, because γ-rays from an RI source do
not have enough brilliance as a parallel beam required for quasielastic scattering
experiments, the method requires much measuring time (e.g., weeks). In this section,
we call the quasielastic scattering spectroscopy using the γ-rays as quasielastic γ-ray
scattering (QEGS) spectroscopy. Recently, high-brilliance SR is available and widely
used for Mössbauer spectroscopy [112]. Using SR, QEGS was demonstrated by some
techniques. First, QEGS using
57 Fe-nuclear Bragg monochromator, which measures
S(q, E), was attempted and demonstrated [113, 114]. Then, QEGS using TDI of
57 Fe
γ-rays, which observes S(q, t), was demonstrated [115]. These methods allowed
a much quicker measurement of the atomic/molecular dynamics than the RSMR
method owing to high brilliance and directivity of the SR sources and technological
development of the high-resolution monochromator [116] and APD detector [24].
2.4.3 Time-Domain Measurement of Quasielastic Scattering
of Mössbauer Gamma Rays Using Synchrotron
Radiation
In this subsection, we introduce quasielastic scattering method using TDI with singleline Mössbauer γ-rays.
In Sect. 2.4.3.1, we introduce NFS experiment with single-line γ-ray emitters. This experiment corresponds to the QEGS experiment without a sample. In
Sect. 2.4.3.2, the corresponding QEGS using TDI with single-line γ-rays is considered. In Sect. 2.4.3.3, we introduce an interpretation of the time spectrum from
space-time diagram. In Sect. 2.4.3.4, we discuss the selectivity of nuclear species for
TDI.
2.4.3.1 Introduction of Nuclear Forward Scattering Using
Time-Domain Interferometry Setup of Single-Line Mössbauer
Gamma Rays
Before the discussion of the QEGS experiment, it is valuable to consider corresponding NFS with two single-line γ-ray emitters because the NFS experiment corresponds to QEGS experiment without a sample and is a basis of QEGS using TDI. The
NFS experimental setup is shown in the upper figure of Fig. 2.18a. The incident SR is
introduced to two identical materials containing
57 Fe with single-line nuclear excitation profile. After transmitting them, the time spectrum of the SR and γ-rays from the
materials are detected by a detector, such as an APD detector, with a time resolution
of ~1 ns. Hereafter, we call the upstream and downstream emitters as γ-ray emitters 1
and 2, respectively. Here, we assume that emitter 1 is driven with a constant velocity
v in the direction of the incident SR wave vector k to change the γ-ray energy from
that of downstream emitter 2 by the Doppler effect. The relation between applied
M. Seto et al.
method is called as RSMR [111]. However, because γ-rays from an RI source do
not have enough brilliance as a parallel beam required for quasielastic scattering
experiments, the method requires much measuring time (e.g., weeks). In this section,
we call the quasielastic scattering spectroscopy using the γ-rays as quasielastic γ-ray
scattering (QEGS) spectroscopy. Recently, high-brilliance SR is available and widely
used for Mössbauer spectroscopy [112]. Using SR, QEGS was demonstrated by some
techniques. First, QEGS using
57 Fe-nuclear Bragg monochromator, which measures
S(q, E), was attempted and demonstrated [113, 114]. Then, QEGS using TDI of
57 Fe
γ-rays, which observes S(q, t), was demonstrated [115]. These methods allowed
a much quicker measurement of the atomic/molecular dynamics than the RSMR
method owing to high brilliance and directivity of the SR sources and technological
development of the high-resolution monochromator [116] and APD detector [24].
2.4.3 Time-Domain Measurement of Quasielastic Scattering
of Mössbauer Gamma Rays Using Synchrotron
Radiation
In this subsection, we introduce quasielastic scattering method using TDI with singleline Mössbauer γ-rays.
In Sect. 2.4.3.1, we introduce NFS experiment with single-line γ-ray emitters. This experiment corresponds to the QEGS experiment without a sample. In
Sect. 2.4.3.2, the corresponding QEGS using TDI with single-line γ-rays is considered. In Sect. 2.4.3.3, we introduce an interpretation of the time spectrum from
space-time diagram. In Sect. 2.4.3.4, we discuss the selectivity of nuclear species for
TDI.
2.4.3.1 Introduction of Nuclear Forward Scattering Using
Time-Domain Interferometry Setup of Single-Line Mössbauer
Gamma Rays
Before the discussion of the QEGS experiment, it is valuable to consider corresponding NFS with two single-line γ-ray emitters because the NFS experiment corresponds to QEGS experiment without a sample and is a basis of QEGS using TDI. The
NFS experimental setup is shown in the upper figure of Fig. 2.18a. The incident SR is
introduced to two identical materials containing
57 Fe with single-line nuclear excitation profile. After transmitting them, the time spectrum of the SR and γ-rays from the
materials are detected by a detector, such as an APD detector, with a time resolution
of ~1 ns. Hereafter, we call the upstream and downstream emitters as γ-ray emitters 1
and 2, respectively. Here, we assume that emitter 1 is driven with a constant velocity
v in the direction of the incident SR wave vector k to change the γ-ray energy from
that of downstream emitter 2 by the Doppler effect. The relation between applied