2 Synchrotron-Radiation-Based Energy-Domain Mössbauer …
59
limited to below 10
5 eV). The energy selectivity of SR allows the measurement of
40 K
Mössbauer spectra, of which the observation is impossible using ordinary radioactive sources because the first excited state of
40 K is not populated by any radioactive
parent nuclides [4]. Additionally, a prominent advantage of Mössbauer spectroscopy
using the energy-tunable SR is the measurement of element (isotope)-specific phonon
energy spectra, which is difficult with RI sources [5]. Furthermore, the combination of electronic and phonon-state measurements generates site-specific phonon
energy spectra [6]. Moreover, high-brilliance SR enables imaging measurement,
high-pressure measurement, the measurement of tiny samples, etc. In particular,
this is advantageous for RSMR measurement, which can measure angle-dependent
energy transfer and, therefore, requires small angular divergence of the probe γ-rays.
As shown, the use of nuclear excitation process and SR has realized unique and
effective spectroscopic methods applicable to vast research areas. Note that nuclear
resonant scattering spectroscopy using SR has two aspects. One is that it enables
the element (isotope)-specific measurement of electronic states and dynamics with
advanced features. The other is the ultranarrow width of the emitted γ-rays. In
Sect. 2.2, as an element (isotope)-specific method for electronic state (and slow
dynamics) measurement, we discuss synchrotron-radiation-based Mössbauer spectroscopy that yields absorption-type Mössbauer spectra [7]. This method enables
advanced measurement using the excellent features of SR, such as Mössbauer
spectroscopic measurement under high pressures. Furthermore, this method gives
absorption-type spectra similar to those obtained by Mössbauer spectroscopy with
RI sources. Since this method was developed in 2009 and the efficiency was much
improved recently [8], we explain the details of this method precisely based on some
recent results obtained using this method, including the comparison of the other
similar methods. In Sect. 2.3, we discuss the nuclear resonant inelastic scattering
(NRIS) spectroscopy that gives element (isotope)- and site-specific phonon densities of states. This method is sometimes called “nuclear inelastic scattering (NIS),”
“nuclear resonant inelastic X-ray scattering (NRIXS),” and “nuclear resonant vibrational spectroscopy (NRVS),” depending on the scientific field. This method has
been very actively applied to research areas, such as condensed matter physics, earth
sciences, and biosciences. Recently, the local structure of active sites in enzymes
has been studied, and these results are introduced. Moreover, site-specific phonon
measurement is explained in addition to element (isotope)-specific phonon measurement. In Sect. 2.4, RSMR using SR is introduced, which uses the ultranarrow width
of the emitted γ-rays with high directivity. As discussed, ultranarrow-width γ-rays
are produced with this method. It means this method uses only a small part (approximately 10
−9 eV) out of the much wider width (approximately in the electron volt
range) of the SR. Even though the small angular divergence of SR is efficient for
the angle-dependent measurement compared with RI sources that emit γ-rays in
all directions, much improvement in the efficacy is possible. We recently achieved
improvement by developing multiline methods and obtained new results on slow
dynamics. The newly developed method is precisely explained, and recent results
obtained using this method are introduced.
59
limited to below 10
5 eV). The energy selectivity of SR allows the measurement of
40 K
Mössbauer spectra, of which the observation is impossible using ordinary radioactive sources because the first excited state of
40 K is not populated by any radioactive
parent nuclides [4]. Additionally, a prominent advantage of Mössbauer spectroscopy
using the energy-tunable SR is the measurement of element (isotope)-specific phonon
energy spectra, which is difficult with RI sources [5]. Furthermore, the combination of electronic and phonon-state measurements generates site-specific phonon
energy spectra [6]. Moreover, high-brilliance SR enables imaging measurement,
high-pressure measurement, the measurement of tiny samples, etc. In particular,
this is advantageous for RSMR measurement, which can measure angle-dependent
energy transfer and, therefore, requires small angular divergence of the probe γ-rays.
As shown, the use of nuclear excitation process and SR has realized unique and
effective spectroscopic methods applicable to vast research areas. Note that nuclear
resonant scattering spectroscopy using SR has two aspects. One is that it enables
the element (isotope)-specific measurement of electronic states and dynamics with
advanced features. The other is the ultranarrow width of the emitted γ-rays. In
Sect. 2.2, as an element (isotope)-specific method for electronic state (and slow
dynamics) measurement, we discuss synchrotron-radiation-based Mössbauer spectroscopy that yields absorption-type Mössbauer spectra [7]. This method enables
advanced measurement using the excellent features of SR, such as Mössbauer
spectroscopic measurement under high pressures. Furthermore, this method gives
absorption-type spectra similar to those obtained by Mössbauer spectroscopy with
RI sources. Since this method was developed in 2009 and the efficiency was much
improved recently [8], we explain the details of this method precisely based on some
recent results obtained using this method, including the comparison of the other
similar methods. In Sect. 2.3, we discuss the nuclear resonant inelastic scattering
(NRIS) spectroscopy that gives element (isotope)- and site-specific phonon densities of states. This method is sometimes called “nuclear inelastic scattering (NIS),”
“nuclear resonant inelastic X-ray scattering (NRIXS),” and “nuclear resonant vibrational spectroscopy (NRVS),” depending on the scientific field. This method has
been very actively applied to research areas, such as condensed matter physics, earth
sciences, and biosciences. Recently, the local structure of active sites in enzymes
has been studied, and these results are introduced. Moreover, site-specific phonon
measurement is explained in addition to element (isotope)-specific phonon measurement. In Sect. 2.4, RSMR using SR is introduced, which uses the ultranarrow width
of the emitted γ-rays with high directivity. As discussed, ultranarrow-width γ-rays
are produced with this method. It means this method uses only a small part (approximately 10
−9 eV) out of the much wider width (approximately in the electron volt
range) of the SR. Even though the small angular divergence of SR is efficient for
the angle-dependent measurement compared with RI sources that emit γ-rays in
all directions, much improvement in the efficacy is possible. We recently achieved
improvement by developing multiline methods and obtained new results on slow
dynamics. The newly developed method is precisely explained, and recent results
obtained using this method are introduced.