Abstract: An NMR spectrometer is utilized in order to determine the magnetic susceptibility of a sample, in which, by means of the sample, a change in the homogeneous magnetic field in the region of a probe substance is effected and the change in the spectrum of the probe substance which is thereby caused is observed. A method known in the art is based on the modulation of the resonance frequency which occurs when the probe substance is caused to rotate about an axis perpendicular to the direction of the magnetic field. The application of this method encounters difficulties with spectrometers whose probe volume is penetrated axially by the magnetic field. In accordance with the invention, by means of the sample (14), a change is produced in the magnetic field along the probe axis in a sample substance (12) preferentially positioned along the direction of the magnetic field.

Abstract: A probe head is provided for nuclear magnetic resonance (NMR) measurements, in particular for use in NMR tomography.

Abstract: A cavity resonator serves to generate magnetic dipole transitions in a sample, for instance for carrying out electron spin resonance measurements. The natural frequency of the cavity resonator (10) is influenced by a reduction in length of the E flux lines. To this end, conductive areas (20) are arranged at the points where the E flux lines are encountered. This results in an increase of the space factor, related to an unchanged specimen volume, and thus in an improvement of the measuring sensitivity.

Abstract: A coupling arrangement for a cavity resonator (10), in particular for measuring the magnetic resonance of a sample (17) located within the cavity resonator (10) comprises a loop (14) for supplying a radio frequency signal to the cavity resonator (10) and exciting in the latter a specific mode of oscillation. For optimizing the coupling of the radio frequency signal, mechanical means are provided, preferably in the form of an axially adjustable screw (16), which permit the surface of the loop (14) to be varied mechanically, and the loop (14) is capacitively coupled with the resonator housing.

Abstract: A specimen head for electron spin resonance and paramagnetic electron resonance measurements, having an annularly cylindrical resonator, with a waveguide being coupled to one of its end walls in such a manner as to excite an H.sub.011 wave. The other end wall is formed by a piston capable of being shifted for tuning, the piston being attached at the end of a hollow piston rod (6) mounted in a bearing block (4), which also contains the resonator (16), in such a manner that it is concentric relative to the axis of the resonator and longitudinally shiftable. The waveguide (13) is attached to the bearing block (4) on that side of the resonator (16) which is opposite the piston (7) and extends along the outside of the bearing block parallel to the piston rod (6) after having been deflected 180.degree..

Abstract: A test head for electron spin resonance and paramagnetic electron resonance measurements comprises a resonator of circular cylindrical shape adapted to accommodate a coaxially arranged test tube, and a waveguide arrangement for exciting the H.sub.011 wave in the resonator, said waveguide arrangement comprising one section having its one end arranged adjacent one face of the resonator and communicating with the resonator via an opening provided in the face in eccentrical arrangement relative to the resonator. In order to enable the coupling coefficient to be varied and, thus, the resonator to be adapted to the waveguide section, the waveguide section carrying a H.sub.1n wave communicates with the resonator via a coupling slot the angular position (.phi.) of which can be varied relative to the radial plane of the resonator passing through its center. Preferably, the waveguide section exhibits a circular cross-section and can be rotated about its axis. It guides the H.sub.

Abstract: A test head for ENDOR-triple experiments comprising a cylindrical cavity resonator provided with means for exciting the TM.sub.110 mode and a spiral arranged in concentric relation to the cavity axis and connected to the inner conductor of a coaxial line. The walls of the cavity resonator (5) are provided at two diametrically opposite points with projections (4) projecting into the interior of the cavity resonator, consisting preferably of a poorly conductive material and extending over the full height of the cavity resonator. The projections are formed by tubes (14) recessed into the walls of the cavity resonator and enclosing sections (20, 21) of the turns of a modulation coil (19) intended for modulating a D.C. magnetic field (B.sub.0) existing in the cavity resonator in vertical relation to the plane comprising the projections.

Abstract: A resonator for electron spin resonance experiments has two cylindrical elements of the same length arranged with their axes parallel to each other and with their end faces in the same plane so that they partly merge with each other. Devices are coupled to each of the two elements for exciting a degenerate TM.sub.010 mode and a degenerate TE.sub.111 mode. In one area of the resonator whose center is at the intersection point of the two planes of symmetry of the resonator, one of which is the intersection plane of the two elements and the other containing the axes of the two elements, the two modes have a mostly vanishing electric field and, for the most part, magnetic fields perpendicular to each other. In this area, there is, at least in one end face of the resonator, an aperture for inserting a test piece.