6
R. Rüffer and A. I. Chumakov
The discovery by R. L. Mößbauer made available a hard γ -ray source with
unprecedented energy resolution E/E 0 ≈ 10
−13 and longitudinal coherence length
l = c τ 0 ≈ 40 m in case of
57 Fe even nowadays only comparable with highest precision laser systems. Those properties made applications such as wavelength standard [11], Hanbury Brown-Twiss [12], interferometry [13, 14], and Lamb shift [15]
feasible. Furthermore, they established spectroscopies on an atomistic scale, which
are element and even isotope sensitive and non-destructive. Applications comprise two main fields, hyperfine spectroscopy and structural dynamics. In hyperfine
spectroscopy NRS is complementary to other nuclear techniques and yields useful
information on atomic, magnetic, and electric properties. Those fields of applications benefit most, which exploit the specific properties of synchrotron radiation
and therefore allow for applications to high pressure, to grazing incidence geometry
(surfaces and multilayers), to single crystals, and to very small samples. Structural
dynamics on a ps to μs time scale as free or jump diffusion as well as rotational
motions can directly be measured in the time domain by nuclear quasi-elastic scattering techniques. On the fast time scale the (partial) phonon density of states is
directly accessible by (nuclear) inelastic scattering techniques.
For the application two cases may be distinguished, (i) excitation of the nuclear
levels by ‘white’ SR with sharp pulses in time (ps) and the successive spectroscopy in
the time domain and (ii) excitation of the nuclear levels by highly monochromatized
radiation (energy width neV to peV defined by the nuclear level width Γ 0 ) with ‘long’
pulses in time (ns to μs) and the successive spectroscopy in the energy domain. Both
are, generally speaking, connected by the Heisenberg uncertainty principle.
A comprehensive overview on the technique, experimental and theoretical, as well
as on applications is given in the review book by Gerdau and de Ward [16]. The theoretical background was laid by Hannon and Trammell [17, 18] and Afanas’ev and
Kagan [19, 20]. A detailed overview on optics may be found by Shvyd’ko [21] and on
Nuclear Condensed Matter Physics by Röhlsberger [22]. An introduction to Mössbauer spectroscopy with applications is given by Gütlich, Bill, and Trautwein [10].
1.1.2 Synchrotron Radiation
Synchrotron radiation became a synonym for all electromagnetic radiation generated
by transverse acceleration of relativistic charged particles. The name dates back to
its first observation in the General Electric 70 MeV synchrotron. In contemporary
synchrotron radiation facilities the particles are accelerated to their nominal energy
by linear accelerators (linacs) and circular accelerators (synchrotrons). Eventually,
the particles are fed into the storage ring where they travel on a stable, closed orbit
and with fixed energy. This procedure allows for defined and optimum properties of
the generated SR for the various applications.
The transverse acceleration in the storage ring is achieved by static transverse
magnetic fields acting on charged particles such as electrons and positrons (see
Fig. 1.1). For an electron, i.e., a particle of charge −e and of momentum p = m · v,
R. Rüffer and A. I. Chumakov
The discovery by R. L. Mößbauer made available a hard γ -ray source with
unprecedented energy resolution E/E 0 ≈ 10
−13 and longitudinal coherence length
l = c τ 0 ≈ 40 m in case of
57 Fe even nowadays only comparable with highest precision laser systems. Those properties made applications such as wavelength standard [11], Hanbury Brown-Twiss [12], interferometry [13, 14], and Lamb shift [15]
feasible. Furthermore, they established spectroscopies on an atomistic scale, which
are element and even isotope sensitive and non-destructive. Applications comprise two main fields, hyperfine spectroscopy and structural dynamics. In hyperfine
spectroscopy NRS is complementary to other nuclear techniques and yields useful
information on atomic, magnetic, and electric properties. Those fields of applications benefit most, which exploit the specific properties of synchrotron radiation
and therefore allow for applications to high pressure, to grazing incidence geometry
(surfaces and multilayers), to single crystals, and to very small samples. Structural
dynamics on a ps to μs time scale as free or jump diffusion as well as rotational
motions can directly be measured in the time domain by nuclear quasi-elastic scattering techniques. On the fast time scale the (partial) phonon density of states is
directly accessible by (nuclear) inelastic scattering techniques.
For the application two cases may be distinguished, (i) excitation of the nuclear
levels by ‘white’ SR with sharp pulses in time (ps) and the successive spectroscopy in
the time domain and (ii) excitation of the nuclear levels by highly monochromatized
radiation (energy width neV to peV defined by the nuclear level width Γ 0 ) with ‘long’
pulses in time (ns to μs) and the successive spectroscopy in the energy domain. Both
are, generally speaking, connected by the Heisenberg uncertainty principle.
A comprehensive overview on the technique, experimental and theoretical, as well
as on applications is given in the review book by Gerdau and de Ward [16]. The theoretical background was laid by Hannon and Trammell [17, 18] and Afanas’ev and
Kagan [19, 20]. A detailed overview on optics may be found by Shvyd’ko [21] and on
Nuclear Condensed Matter Physics by Röhlsberger [22]. An introduction to Mössbauer spectroscopy with applications is given by Gütlich, Bill, and Trautwein [10].
1.1.2 Synchrotron Radiation
Synchrotron radiation became a synonym for all electromagnetic radiation generated
by transverse acceleration of relativistic charged particles. The name dates back to
its first observation in the General Electric 70 MeV synchrotron. In contemporary
synchrotron radiation facilities the particles are accelerated to their nominal energy
by linear accelerators (linacs) and circular accelerators (synchrotrons). Eventually,
the particles are fed into the storage ring where they travel on a stable, closed orbit
and with fixed energy. This procedure allows for defined and optimum properties of
the generated SR for the various applications.
The transverse acceleration in the storage ring is achieved by static transverse
magnetic fields acting on charged particles such as electrons and positrons (see
Fig. 1.1). For an electron, i.e., a particle of charge −e and of momentum p = m · v,