The Electron Spin Resonance Facility
A Bruker ESP300E spectrometer is available for the measurement of electron spin (paramagnetic) resonance in materials over a wide range of physical conditions. The machine is situated in Room S105 (Tel: 88142) and is operated under the supervision of Dr Chris Adams.
Anyone who may have a paramagnetic sample which could give an ESR spectrum should first consult with Dr Adams who will advise on the best way to conduct the measurements. Dr Adams will also train research workers in the use of the spectrometer should they need to measure spectra routinely. The machine is relatively easy to ‘drive’!
The ESP300E is an X-Band spectrometer. It operates at 9-10 GHz and magnetic fields of 0.35 T for samples with g = 2; the 25 cm electromagnet allows field measurements of up to 1.2 T. The X-band Gunn Diode microwave source provides power up to 200 mW. The spectrometer has three microwave cavities: an ER102ST rectangular resonator for normal measurements; an ER4122 cylindrical (high Q) resonator for weak samples; an ER4104OR optical transmission resonator enabling uv/visible spectra to be measure in situ. Rapid scan measurements (50 Hz) are also possible over small field ranges (10 mT).
Samples can be run under various conditions:
- In silica tubes up to 10 mm o.d., but any material free of paramagnetic impurities can be used provided the tube is less than 10 mm diameter.
- At temperatures between 77 K (liquid N2 Dewer) and between 100 K and 500 K with variable temperature system. Measurements can be made down to 4 K by arranging a liquid helium supply.
- In flat cells for the measurement of aqueous solutions or other solutions with a high dielectric.
Tubes can usually be supplied for initial measurements on unknown samples. However, in the longer term these must be supplied by the users of the machine.