Mossbauer Spectroscopy

Mössbauer spectroscopy is a type of nuclear spectroscopy involving the resonant emission and absorption of γ-rays (also known as the Mössbauer effect). This effect requires a "recoil-free" nuclear transition in which no net change in momentum is imparted to the nucleus. This means the technique is applicable only for solids and frozen solutions. Mössbauer spectroscopy is specific to ⁵⁷Fe, a stable Fe isotope with a natural abundance of 2.12%. It is by far the most studied isotope (~95% of the studies).

Mössbauer spectroscopy provides information about valence state, coordination number, and magnetic ordering temperatures. In contrast to X-ray diffraction, Mössbauer spectroscopy also provides information on compounds that do not exhibit long-range order, such as poorly crystalline or amorphous materials.

This versatile, highly sensitive, and nondestructive technique has a wide range of applications in various fields including soil science, geochemistry, aerosols, and materials science. The primary uses of ⁵⁷Fe-Mössbauer spectroscopy at EMSL are to study the effect of Fe redox chemistry and mineralogy on the bioavailability of organic matter (OM) in various soil systems (e.g., rhizosphere, subsurface, floodplain, marine, and coastal environments). These studies strengthen or challenge the existing conceptual models of soil OM stabilization (with focus on mineral-OM associations), help predict Fe and P dynamics of deposited aerosols and smoke particles, identify the Fe species responsible for activity in catalytic systems, and characterize the reactive Fe species driving attenuation of soluble radionuclides in contaminated soils and the nature of Fe-doped glasses.

Research application

• Mössbauer spectroscopy supports the Terrestrial-Atmospheric Processes Integrated Research Platform by assisting researchers with detailed bulk Fe mineralogical analysis, furthering their understanding of biogeochemical reactions and fluxes within soil and aerosol research areas.
• Mössbauer spectroscopy supports the Biogeochemical Transformations Integrated Research Platform in its mission to answer fundamental questions related to how changes in Fe speciation affect the transformation and mobility of carbon and nutrients within the environment.

Available Instruments

• SEE Co (Edina, MN) and WissEl (Germany) Mössbauer spectrometers
• Closed-cycle refrigerant cryostat systems (sHI-850; Janis Research Co, Inc., Wilmington, MA) and Sumitomo CKW-21 He compressor units

Tips for success

• All work with the Mössbauer spectroscopy system must be performed in compliance with EMSL practices and permits.