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Bruker Biospin Gmbh

Peter Höfer

Ion Prisecaru

Patrick Carl

A microwave resonator for an electron paramagnetic resonance probehead comprises a cavity body supporting an electromagnetic microwave resonance mode, at least one sample opening for inserting a sample in a sample container, at least one microwave opening for transmitting microwave radiation into the resonator, and at least one access opening for inserting and removing a modifier in a modifier vessel into or out of the cavity body. The modifier vessel is fixed in the at least one access opening, the modifier is a fluid comprising attenuator fluid and/or marker fluid and/or adaptor fluid, and the modifier vessel has an insert opening for filling and discharging the modifier gradually into or out of the cavity body. This improves performance greatly, enabling a gradual modification of specific experimental conditions without moving any mechanical parts in the cavity body, and without changing other experimental conditions for Q- and/or M- and/or D-variation.

Microwave resonator for an EPR probehead providing Q-, M- and D-variation using a variable fluid volume

In a method for determining an absolute number of electron spins in an extended sample () with the assistance of an apparatus for measuring magnetic resonance, the extended sample () is disposed within a measurement volume () of a radiofrequency RF resonator () of the apparatus during an electron spin resonance measurement (ESR). The method has the following steps: determining a spatial sensitivity profile f of the RF resonator () over the measurement volume (); determining a resonator sensitivity constant c by means of a comparison to the measurement volume () of small calibration sample having a known number of electron spins at a particular position within the measurement volume (); measuring a magnetic resonance signal RS of the extended sample () in the apparatus with a known spatial distribution of extended sample () within the measurement volume (); weighting the magnetic resonance signal RS with the integral of the spatial sensitivity profile f of the RF resonator over the partial volume of the measurement volume () occupied by the extended sample (); and determining the number of electron spins Nin extended sample () as a quotient between the weighted resonance signal and the resonator sensitivity constant c. The method facilitates a simpler determination of the absolute number of electron spins in the sample.

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Ettlingen, Germany

Peter Höfer