The core principle of Mössbauer spectroscopy involves a gamma-ray source moving relative to a sample containing the same isotope as the source. By varying the velocity of the source, the Doppler effect shifts the energy of the emitted gamma rays. When the energy of the emitted gamma ray precisely matches an absorption energy of a nucleus in the sample, resonance absorption occurs. This resonance absorption is detected, and the resulting spectrum, which plots absorption intensity against source velocity, reveals information about the nuclear environment.
Key parameters extracted from a Mössbauer spectrum include the isomer shift, quadrupole splitting, and magnetic hyperfine splitting. The isomer shift is sensitive to the electron density at the nucleus, providing insights into the oxidation state and chemical bonding of the Mössbauer isotope. Quadrupole splitting arises from the interaction between the nuclear quadrupole moment and an electric field gradient at the nucleus, indicating the symmetry of the electronic environment and the presence of non-spherical charge distributions. Magnetic hyperfine splitting occurs when the nucleus experiences a magnetic field, revealing magnetic ordering and spin states within the material.
Mössbauer spectroscopy is particularly useful for studying iron-containing compounds, tin compounds, and other isotopes exhibiting the Mössbauer effect. Its applications span a wide range of scientific disciplines, including solid-state physics, chemistry, materials science, mineralogy, and even biology. It can be used to characterize the phase purity and composition of materials, investigate magnetic properties, study diffusion processes, and determine the structure and bonding in complex chemical systems. The technique is non-destructive and can be performed on various sample forms, including solids, powders, and even frozen solutions.