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ArrowElectron Magnetic Resonance (EMR) Overview


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What is EMR?

The acronym EMR stands for Electron Magnetic Resonance, which covers a variety of magnetic resonance techniques associated with the electron. Most popular of those techniques is Electron Paramagnetic/Spin Resonance (EPR/ESR). In simplified terms, EPR/ESR can be performed on any sample that has unpaired electron spins. More details and explanations on EMR including EPR/ESR can be found here. EPR/ESR has proven an indispensable tool in a large range of applications in physics, materials science, chemistry and biology, including studies of impurity states, molecular clusters, antiferromagnetic, ferromagnetic and thin film compounds, natural or induced radicals, optically excited paramagnetic states, electron spin-based quantum information devices, transition-metal based catalysts; and for structural and dynamical studies of metallo-proteins, spin-labeled proteins and other complex bio-molecules and their synthetic models.

Why High Frequencies and Fields?

For historic and technological reasons most EPR/ESR research has been done at the X-Band frequency of ~9.5 gigahertz (GHz). Q-Band (35 GHz), W-Band (95 GHz) and D-band (130-140 GHz) instruments are also commercially available, with a recent addition of a 263 GHz spectrometer by Bruker to their offer. Frequencies up to, and beyond 1 terahertz (THz) and magnetic fields of several teslas and more offer numerous advantages over conventional techniques:

Multifrequency EMR
A multifrequency set of EPR spectra in a high-spin Ni(II) complex HB(tBuIm)3NiBr (frequencies indicated on the plot).

Instrumentation

The Electron Magnetic Resonance (EMR) facilities offer users several home-built, high-frequency and high-field continuous-wave (c.w.) instruments providing frequency coverage from 9 GHz to 1 THz, with additional frequencies available up to 2.5 THz using a molecular gas laser. Several transmission probes are available for measurements that are compatible with a range of magnets at the lab, including the highest field 45 T hybrid. Some of the probes can be configured with resonant cavities, providing enhanced sensitivity as well as options for in-situ rotation of samples in the magnetic field.

The pulsed EPR/ESR spectrometer offers a time resolution of 100 ns at the highest currently available frequency in the world, 336 GHz. EPR/ESR has proven an indispensable tool in a large range of applications in physics, materials science, chemistry and biology, including studies of impurity states, molecular clusters, antiferromagnetic, ferromagnetic and thin film compounds, natural or induced radicals, optically excited paramagnetic states, electron spin-based quantum information devices, transition-metal based catalysts; and for structural and dynamical studies of metalloproteins, spin-labeled proteins and other complex bio-molecules and their synthetic models.

The list of particular spectrometers together with their basic characteristics can be found below. The links will lead to a detailed description of the particular instrument including sample requirements and principal applications.

Collected parameters of the above instruments can also be found in this table.

More high-frequency EMR spectrometers are available to collaborative research in the laboratory of Prof. Stephen Hill.

We also continue to develop new instruments.

EMR Users

The EMR users represent one of the most interdisciplinary groups at the MagLab. The facility typically publishes 25 to 45 peer-reviewed journal articles each year, with many in high-impact journals such as Nature, Science and Physical Review Letters. Roughly half of the group's publications appear in American Physical Society journals, with the remainder appearing in chemistry and biology journals. The EMR group is able to provide some financial support for visits to the MagLab by first-time users.


For more information contact EMR program director Stephen Hill.


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