Chemistry Reference
In-Depth Information
Fig. 2.30
57
Fe Mössbauer
spectra of the mesogen
[Fe(C
10
-tba)
3
](4-
MeC
6
H
4
SO
3
)
2
nH
2
O, with
n = 1 at 4.2 K (a)ofn = 0at
200 K (b) and of n = 0at
4.2 K (c)[
53
,
54
]
experiment one uses a single-line absorber (free of electric quadrupole and magnetic
dipole interaction), e.g. K
4
[Fe(CN)
6
], and a
57
Co doped sample under study as
source. In this case, the recorded Mössbauer spectrum refers to the hyperfine inter-
actions in the source material, i.e. it yields information on the chemical and physical
properties of the excited
57
Fe atoms before they decay to the ground state. The MES
technique has been widely used to investigate chemical and physical after-effects of
nuclear decay in various materials, particularly in coordination compounds [
59
]. The
electron capture decay of radioactive
57
Co, whereby an electron from the K-shell is
captured by the
57
Co nucleus leading to
57
Fe,
57
Co(EC)
57
Fe, may lead to a variety of
after-effects like bond rupture, ligand radiolysis, change of charge states and excited
ligand field states to name the most important consequences of nuclear decay in solid
coordination compounds. These after-effects may have lifetimes on the order of
10-500 ns. It is possible to cover this time regime and study the relaxation kinetics of
such
short-lived
after
effect
species
with
time-integral
and
time-differential
Mössbauer emission spectroscopy [
60
,
61
].
