J.A.J.M. Disselhorst

Electron spin-echo spectroscopy at 95 GHz

Abstract An electron spin-echo spectrometer operating at 94.9 GHz is described. The experimental details of the microwave circuit are discussed and the performance is compared with that of more conventional spectrometers at 9.5 GHz.

An insert for single‐molecule magnetic‐resonance spectroscopy in an external magnetic field

We describe an insert for optical and magnetic‐resonance experiments on single molecules in a solid matrix at liquid‐helium temperatures. The experimental arrangement allows in situ adjustment of the focusing lens and of the sample. A parabolic mirror serves to collect the fluorescence emission and to direct the light onto a photodetector. Microwaves can be irradiated through a coil around the sample while a superconducting magnet provides the possibility of a stationary magnetic field.

Continuous-wave EPR at 275 GHz: Application to high-spin Fe3+ systems

The 275GHz electron-paramagnetic-resonance spectrometer we reported on in 2004 has been equipped with a new probe head, which contains a cavity especially designed for operation in continuous-wave mode. The sensitivity and signal stability that is achieved with this new probe head is illustrated with 275GHz continuous-wave spectra of a 1mM frozen solution of the complex Fe(III)-ethylenediamine tetra-acetic acid and of 10mM frozen solutions of the protein rubredoxin, which contains Fe(3+) in its active site, from three different organisms. The high quality of the spectra of the rubredoxins allows the determination of the zero-field-splitting parameters with an accuracy of 0.5GHz. The success of our approach results partially from the enhanced absolute sensitivity, which can be reached using a single-mode cavity. At least as important is the signal stability that we were able to achieve with the new probe head.

A low-temperature insert for a 95 GHz electron-spin-echo spectrometer

The construction is described of an insert that allows electron-spin-echo experiments to be performed on photo-excited paramagnetic states in single crystals at liquid helium temperatures at a resonance frequency of 95 GHz.

A loop-gap resonator for microwave-induced optical nuclear polarization, electron spin-echo experiments, and dynamic nuclear polarization

Abstract A special double loop-gap resonator for CW and pulsed EPR experiments at X band is presented. It allows for simultaneous optical access, high uniaxial pressure on the sample, and NMR and EPR experiments at liquid helium temperatures. It is used for microwave-induced optical nuclear polarization in semiconductors.

Continuous-wave EPR at 275GHz: Application to high-spin Fe3+ systems

The 275GHz electron-paramagnetic-resonance spectrometer we reported on in 2004 has been equipped with a new probe head, which contains a cavity especially designed for operation in continuous-wave mode. The sensitivity and signal stability that is achieved with this new probe head is illustrated with 275GHz continuous-wave spectra of a 1mM frozen solution of the complex Fe(III)-ethylenediamine tetra-acetic acid and of 10mM frozen solutions of the protein rubredoxin, which contains Fe(3+) in its active site, from three different organisms. The high quality of the spectra of the rubredoxins allows the determination of the zero-field-splitting parameters with an accuracy of 0.5GHz. The success of our approach results partially from the enhanced absolute sensitivity, which can be reached using a single-mode cavity. At least as important is the signal stability that we were able to achieve with the new probe head.

A modification of the commercial ESR900 cryostat to enable three-dimensional electron-paramagnetic-resonance studies of crystals

Complete orientation studies of X-band electron-paramagnetic-resonance spectra of crystals largely benefit from the possibility to measure the spectrum for any orientation of the magnetic field with respect to the crystal without the need to remount the crystal. We report on a modification of a commercial cryostat to allow such experiments down to liquid helium temperatures and demonstrate its performance.