EMR Facility Developments
A new EMR lab will come online in the summer of 2009 with two new multi-high-frequency (8-700 GHz), high-field instruments. In addition, several new (funded) capabilities are planned for the next one to two years, including: a Mössbauer spectrometer; a superheterodyne spectrometer based on solid-state sources providing continuous frequency coverage from X-band to 1 THz; a triple-axis superconducting vector magnet system; and sub-Kelvin temperatures. The broadband capabilities will immediately be compatible with the DC resistive magnets, including the 45 T hybrid; a longer term goal is to develop a frequency domain spectrometer compatible with the high-field resistive split-gap magnet that is currently under development at the Mag Lab. We also plan to develop a low-temperature EMR capability for the resistive facility.
Mössbauer Spectroscopy
The EMR group has recently acquired a Mössbauer spectrometer that will eventually operate in conjunction with a 9 T magnet. This technique involves the absorption by 57Fe (2.2% natural abundance) of 14.4 keV gamma radiation produced by a radioactive 57Co source (the 57Co decays via electron capture to 57Fe); by measuring the Doppler-shifted absorption in Fe containing materials, one can deduce important structural and chemical information. For example: The isomer shift is related to the electron density at the nucleus which, in turn, provides information concerning the Fe oxidation state, i.e. its spin state; the electric quadrupolar interaction splits the spectrum and provides information about electric field gradients and the site symmetry at the nucleus; and the nuclear Zeeman interaction further splits the spectrum, enabling studies of the local magnetism. This new experimental capability will enable: iron detection and recognition of minerals containing iron; determination of iron valence states, structures and bonding in compounds; and analysis of magnetic properties of compounds and alloys, including internal magnetic field detection in ferromagnets.
For more information, see the article Mag Lab establishes Mössbauer spectroscopy facility (PDF) from Mag Lab Reports (Vol. 16, No. 3).
Enhanced Pulsed EPR Capabilities
An important goal of the group involves improving the temporal resolution of our high-frequency pulsed instrument. We are working with groups in the US and Europe to procure high-power microwave sources/amplifiers and develop the needed quasioptical components to build the next generation pulsed spectrometer for the Mag Lab operating above 200 GHz, with an ultimate goal of nanosecond time resolution.
The EMR group continues to be very active in developing a proposal to support construction of a fourth-generation THz/infrared accelerator-based light source at the DC field facility in Tallahassee. The Big Light design offers unique measurement capabilities: three co-located narrow-band tunable sources with overlapping frequency ranges spanning the full terahertz-to-Infrared (THIR) regime from 0.3 to 120 THz; an overlapping, co-located broadband THz source (0.1 – 3 THz); ultra-fast (1 ps) light pulses with a 10 MHz repetition rate; ultra-high brightness (106 times brighter than 3rd generation synchrotrons); and, finally, automatic time-synchronization of near-IR, mid-IR and THz pulses (< 20 fs jitter for multi-color, pump-probe experiments).
For more information contact EMR program director Stephen Hill.
