84
M. Seto et al.
Fig. 2.16 Time and length regions of fluctuations covered by various quasielastic scattering techniques. Quasielastic scattering technique using 14.4-keV γ-rays from 57 Fe nuclei covers a unique
timescale and length scale
because the Mössbauer effect is used to generate the γ-rays with very high energy
resolution and the γ-rays are used for the probe of nonresonant quasielastic scattering
study. In Fig. 2.16, we show established time and length regions of the fluctuations
that can be studied by quasielastic scattering with 14.4-keV γ-rays from
57 Fe nuclei.
This section is composed of the following subsections: In Sect. 2.4.2, basic
concepts of quasielastic scattering by nonresonant samples are introduced. In
Sect. 2.4.3, the conventional time-domain measurement technique of quasielastic
scattering using time-domain interferometry (TDI) with single-line Mössbauer γrays is discussed. In Sect. 2.4.4, a finite energy width of incident SR is considered,
and the effect on the time spectrum of single-line γ-ray quasielastic scattering is
introduced. In Sect. 2.4.5, quasielastic scattering using TDI with multiline Mössbauer
γ-rays is described, and its advantage is summarized. In Sect. 2.4.6, results using
γ-ray quasielastic scattering are presented. In Sect. 2.4.7, summary and perspective
of γ-ray quasielastic scattering are discussed.
2.4.2 Basic Concept of Quasielastic Scattering
by Nonresonant Samples
We consider the Rayleigh scattering process of the Mössbauer γ-rays, whose wave
vector is k, by electrons in a sample, such as liquids. Hereafter, we mainly consider
the 14.4-keV Mössbauer γ-rays with 4.66-neV energy width from the first nuclear
excited state of
57 Fe. In the scattering geometry shown in Fig. 2.17, the γ-rays transfer
a momentum q =
k
− k
= 2k sin θ to the sample, where k
is the wave vector of
the scatted γ-rays and 2θ is the scattering angle. In the elastic Rayleigh scattering
case, it follows that |k| ∼
k
. In a simple mono-atom liquid, an electron density
M. Seto et al.
Fig. 2.16 Time and length regions of fluctuations covered by various quasielastic scattering techniques. Quasielastic scattering technique using 14.4-keV γ-rays from 57 Fe nuclei covers a unique
timescale and length scale
because the Mössbauer effect is used to generate the γ-rays with very high energy
resolution and the γ-rays are used for the probe of nonresonant quasielastic scattering
study. In Fig. 2.16, we show established time and length regions of the fluctuations
that can be studied by quasielastic scattering with 14.4-keV γ-rays from
57 Fe nuclei.
This section is composed of the following subsections: In Sect. 2.4.2, basic
concepts of quasielastic scattering by nonresonant samples are introduced. In
Sect. 2.4.3, the conventional time-domain measurement technique of quasielastic
scattering using time-domain interferometry (TDI) with single-line Mössbauer γrays is discussed. In Sect. 2.4.4, a finite energy width of incident SR is considered,
and the effect on the time spectrum of single-line γ-ray quasielastic scattering is
introduced. In Sect. 2.4.5, quasielastic scattering using TDI with multiline Mössbauer
γ-rays is described, and its advantage is summarized. In Sect. 2.4.6, results using
γ-ray quasielastic scattering are presented. In Sect. 2.4.7, summary and perspective
of γ-ray quasielastic scattering are discussed.
2.4.2 Basic Concept of Quasielastic Scattering
by Nonresonant Samples
We consider the Rayleigh scattering process of the Mössbauer γ-rays, whose wave
vector is k, by electrons in a sample, such as liquids. Hereafter, we mainly consider
the 14.4-keV Mössbauer γ-rays with 4.66-neV energy width from the first nuclear
excited state of
57 Fe. In the scattering geometry shown in Fig. 2.17, the γ-rays transfer
a momentum q =
k
− k
= 2k sin θ to the sample, where k
is the wave vector of
the scatted γ-rays and 2θ is the scattering angle. In the elastic Rayleigh scattering
case, it follows that |k| ∼
k
. In a simple mono-atom liquid, an electron density