EMR

EMR is the electronic counterpart of NMR (Nuclear Magnetic Resonance). This kind of spectroscopy is particularly suited to detect and microscopically identify atomic or molecular systems with unpaired electrons (paramagnetic centers). EMR includes in the first place the basic technique, i.e., EPR (Electron Paramagnetic Resonance), also known as ESR (Electron Spin Resonance) but also derived techniques as ENDOR (Electron Nuclear DOuble Resonance) and EIE (ENDOR induced EPR). For instance with ENDOR, NMR transitions can be observed via the EPR signal, with an inherently better sensitivity than with NMR itself.

On the one hand, EMR allows a high level detailed characterization of paramagnetic centers (symmetry, electron spin, valence state, chemical identity and electronic and geometrical structure of direct environment, etc.). On the other hand, by its high sensitivity (about 1010 paramagnetic centers in absolute terms), reproducibility and non-destructive character, EPR has also important applications in the field of radiation dosimetry, dating and detection of irradiation in foodstuffs.

Comparable to NMR, EMR makes use of an (electronic) magnetic moment that interacts with external or internal magnetic fields, e.g., due to neighboring nuclear spins. EMR transitions are of the magnetic dipole type and occur between electronic levels split by Zeeman or hyperfine interactions. They are induced by microwave radiation (mm/cm region). The area of application is very broad and includes among others biology, chemistry, physics, geology, medecine, pharmacy, material science and agriculture. Although within the UGent Department of Solid State Sciences, the research on defects and radicals in solids prevails, the sample can also be liquids or even gases (typical dimension of a few mm3).

At the moment the EMR group disposes of EPR, ENDOR and EI-EPR in X and Q-band (microwaves with frequencies around 9.5 GHz and 34 GHz respectively), supplemented with extensive peripheral equipment, e.g., for cryogenics and in situ irradiation (optical and UV region).

The research of the EMR group is at present mainly directed towards radiation damage in DNA and bio-organic model systems (sugars, amino acids, etc.), and towards catalytically relevant defects in MOFs (Metal Organic Frameworks) (see running project of the group). Via projects in the (recent) past, the group has acquired important expertise in the field of defects and radicals in apatites, transition metal or lanthanide activated optical materials (phosphors) and semiconductors (in close collaboration with the DISC research group).

Key words : EMR, EPR, ENDOR, EIE, radicals, DNA, sugars, amino acids, MOFs, catalysis, dosimetry