The present invention relates to a magnetic resonance device, a magnetic resonance system, a magnet device and a magnetic resonance method.
Nuclear magnetic resonance (NMR) is a technique that can provide structural information with remarkable detail. The scope of applications includes the study of the structure and dynamics of organic molecules and biomolecules in solution, as well as the study of solid materials such as crystalline proteins, carbon-based anodes, nitrogen-vacancy centers of diamonds, amorphous silica powder and many more. Electron paramagnetic resonance (EPR) works according to similar principles as NMR and provides information such as function and structure of radical enzymes, dynamics of proteins and in operandi studies of lithium ion batteries.
NMR resonance lines of static samples in the solid state are much broader than in solution due to anisotropic interactions experienced by the nuclei, critically degrading spectral resolution. Dominant contributions to linewidth in NMR originate from dipolar spin-spin couplings, chemical shift anisotropy and quadrupolar couplings in spin l>1/2 systems. In solution, these anisotropic actions are averaged out by rapid molecular motions. Anisotropic interactions also broaden the resonance lines of solids in EPR, with linewidths that are several orders of magnitude larger than typical solution-state linewidths in spin 1/2 systems in NMR.
Spinning the sample about a spinning axis of the sample at the magic angle Θm=arctan √{square root over (2)}≈54.74° (“magic-angle spinning”, MAS) partially averages the aforementioned anisotropic interactions. To spin a sample at the magic angle, the sample is packed into a cylindrical or spherical rotor, and the rotor is spun in the probe pneumatically. For cylinders, both drive and bearing gas are necessary for stable spinning, while one gas stream suffices for spheres.
Over the last decades, pneumatically driven MAS has become a standard technique for high resolution solid-state NMR Since higher spinning frequencies result in sharper resonance lines, much effort has been spent to maximize the MAS frequency. MAS frequencies up to 170 kHz have been reported [Samoson2019].
Still higher frequencies would be needed to fully average 1H-1H dipolar couplings or quadrupolar couplings in NMR or to sufficiently average anisotropic interactions in EPR. Higher spinning frequencies would also improve spin relaxation properties, which would enable better control over spins in NMR and EPR and would improve dynamic nuclear polarization (DNP), a technique which improves NMR sensitivity. Such gains in NMR and EPR performance could be employed, for instance, in the structural and motional characterization of molecular architectures of interest in biology and chemistry.
it is an object of the present invention to provide a magnetic resonance device that enables sample spinning at higher frequencies than hitherto possible.
This object is achieved by a magnetic resonance device according to claim 1, Further embodiments of the invention are laid down in the dependent claims.
In a first aspect, the present invention provides a magnetic resonance device comprising:
In to the present invention, electromagnetic energy is used to provide torque about the sample spinning axis for the spinning of samples in magnetic resonance experiments, With this invention, experiments can be performed in vacuum, or at low pressures, and the maximum spinning frequency will be limited only by the structural mechanical strength of the spinning object or the friction with the remaining gas molecules. MAS at spinning frequencies up to several gigahertz can in principle be achieved, enabling unprecedented spectral resolution in solid-state magnetic resonance spectroscopy. Also, spinning about two angles simultaneously (double angle spinning) can be implemented using the present invention by providing torque about a second axis.
In some embodiments, the sample spinning field comprises an oscillating electromagnetic field, in particular, a propagating or standing electromagnetic wave, that is circularly polarized so as to exert the torque on the sample by transfer of spin angular momentum from the electromagnetic field to mechanical angular momentum of the sample. In other embodiments, torque may be created by off-center irradiation of the sample with electromagnetic radiation, thus transferring linear momentum on the sample at a distance from the rotation axis by radiation pressure. Torque may also be created by a rotating electric field.
In some embodiments, the sample spinning field comprises light having a frequency above 30 THz, and the sample spinning apparatus comprises:
In other embodiments, the sample spinning field comprises a microwave field having a frequency below 30 THz, and the sample spinning apparatus comprises:
The sample spinning apparatus may further be configured to confine (“trap”) the sample at the sample location along one, two or three spatial directions by interaction of the sample with the sample spinning field and/or with an electromagnetic trapping field that is different from the sample spinning field. In some embodiments, the trapping field may comprise light having a frequency above 30 THz. Trapping and spinning of particles using light is known per se, and spinning frequencies of up to several GHz have been reported, see. e.g., [Monteiro2018], [Reimann2018] or [Jin2021]. In other embodiments, the trapping field may comprise a microwave field having a frequency below 30 THz, Trapping by microwaves has been described, e.g. in [Lewelling2018] and [Wright2019]. In yet other embodiments, electric fields may be used for confining the sample, as in a Paul trap.
The magnetic resonance device may further comprise a sample support structure configured to support the sample in addition to or in lieu of the electromagnetic trapping field, in some embodiments, the sample support structure may comprise one of the following structures:
For carrying out magnetic resonance experiments, the magnetic resonance device may further comprise an excitation apparatus coupled to the resonance structure to create the excitation field and/or a detection apparatus for detecting a response of the sample to the excitation field. The detection apparatus may comprise detection circuitry coupled to the resonance structure to detect a response of the sample to the excitation field through interaction of the sample with the resonance structure. In other embodiments, the detection apparatus may be configured to detect said response indirectly, e.g., optically, as it is known per se.
The resonance structure may be configured as a chip, comprising a flat carrier, in particular, a printed circuit board or a semiconductor chip, the carrier defining a carrier plane. If the sample spinning field comprises light, the carrier plane may be parallel to a direction of propagation of the light at the sample location, or the carrier plane may be transverse to the direction of propagation of the light at the sample location, the carrier having a hole to allow the light to pass through the carrier.
The magnetic resonance device may further comprise a vacuum chamber, and the sample location may be arranged inside the vacuum chamber to enable the sample to be spun in a vacuum.
By its design, the magnetic resonance device may be configured to expose the sample to a static magnetic field that defines a static field direction. In particular, the magnetic resonance device may be configured to be arranged relative to the static magnetic field in such a manner that the sample spinning axis has an orientation at the magic angle Θm=arctan √{square root over (2)} relative to the static field direction. In some embodiments, the magnetic resonance device may be configured to be inserted into a cylindrical bore of a superconducting magnet device such that the sample location is arranged inside the cylindrical bore. To this end, the magnetic resonance device may comprise a cylindrical probe body in which the sample location is arranged. The cylindrical probe body may define a cylinder axis, and the sample spinning axis may then have an orientation at the magic angle relative to the cylinder axis of the cylindrical probe body. When the magnetic resonance device is inserted into the cylindrical bore, the cylinder axis of the cylindrical probe body may coincide with a longitudinal axis of the cylindrical bore. The outer diameter of the cylindrical probe body may match the inner diameter of the cylindrical bore such that it is possible to insert the cylindrical probe body into the cylindrical bore.
The present invention further provides a magnetic resonance system that actually comprises a magnet device for generating the static magnetic field along a static field direction.
In some embodiments, the sample spinning axis may be vertical or horizontal in space (i.e., parallel or perpendicular to the direction of gravity, i.e., the direction of the earth's gravitational field), and the static field direction is inclined to the sample spinning axis by the magic angle Θm. In other embodiments, the static field direction is vertical or horizontal in space, and the sample spinning axis is inclined to the static field direction by the magic angle.
In another aspect, the present invention provides a magnet device that is configured to be used in conjunction with the magnetic resonance device of the present invention. The magnet device comprises a ring-shaped superconducting magnet having a ring axis that is inclined to the direction of gravity by the magic angle Θm=arctan √{square root over (2)} The superconducting magnet is configured to generate a static magnetic field having a static field direction that coincides with the ring axis. The magnet device may comprise a support for supporting the magnet device in such a manner that the ring axis that is inclined to the direction of gravity by the magic angle when the support is placed on a level floor.
In some embodiments, the magnet device comprises a disk-shaped magnet cryostat that defines a liquid helium bath in which the superconducting magnet is immersed, the disk-shaped magnet cryostat having a central bore along the ring axis, commonly called a “room-temperature bore”, for providing access for the sample such that the sample can be exposed to the static magnetic field outside the liquid helium bath. The central bore is preferably configured such that a straight laser beam can be passed through the central bore at the magic angle to the ring axis, in particular, along the direction of gravity, without the beam intersecting the disk-shaped magnet cryostat. In particular, the central bore may be of cylindrical shape. It may have a diameter D and a length L, along the ring axis, wherein the diameter D and the length L have a ratio D/L>√{square root over (2)}.
In some embodiments, the magnet device further comprises:
The auxiliary cryostat may further comprise a liquid nitrogen reservoir. The liquid nitrogen reservoir may at least partially surround the liquid helium reservoir to protect the auxiliary liquid helium reservoir from thermal radiation.
In advantageous embodiments, the disk-shaped magnet cryostat comprises a metallic radiation shield element comprising a shielding portion and a contact portion, the shielding portion being arranged in a vacuum between two shells of the disk-shaped magnet cryostat and at least partially surrounding the liquid-helium bath so as to protect the liquid helium bath from thermal radiation, and the contact portion being immersed in the liquid nitrogen reservoir of the auxiliary cryostat.
In another aspect, the present invention provides a magnetic resonance method comprising:
Unlike in traditional MAS, where pressurized air is used to spin a rotor in which the sample is packed. no separate rotor is needed in the present invention, and the sample can be spun without being packed in a rotor. In particular, the sample may be a single particle, or it may comprise multiple particles that are individually rotated. However, the use of a rotor for packing the sample is not excluded. In some embodiments, the sample may be approximately spherical. The presently proposed method is particularly well suited for spinning samples having a diameter of not more than 1 mm. However, the method is not limited to such small samples, and sample size can reach 10 mm, 20 mm or even more.
Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,
The term “magnetic resonance” encompasses nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR), which is sometimes also called electron spin resonance (ESR).
The term “B0 field” relates to a static magnetic field that causes a Zeeman splitting of nuclear and/or electronic spins in a sample. The direction of the B0 field is called the z direction. In practice, the B0 field is often created by a superconducting magnet in a cryostat.
The term “B1 field” relates to an oscillating electromagnetic field that is able to change at least one spin state in the sample when the sample is exposed to the B0 field. The B1 field is normally applied at or near the Larmor frequency ωL, =γB0 of the spin species whose spin state is to be modified, where γ is the gyromagnetic ratio of the spin species.
The term “electromagnetic field” is to be understood broadly as encompassing static and time-dependent electric fields, static and time-dependent magnetic fields, and combinations thereof.
The magnetic resonance system comprises a magnet device 10 comprising a ring-shaped (annular) superconducting magnet 11 having a ring axis A for creating a static magnetic field B0 along a static field direction z. The ring-shaped superconducting magnet 11 is received in a flat: disk-shaped magnet cryostat 12 defining a cylindrical central room temperature bore along the ring axis of the magnet 11. The magnet cryostat 12 is connected to an auxiliary cryostat 16. Further details of the superconducting magnet 11, the magnet cryostat 12 and the auxiliary cryostat 16 will be provided below. The direction z of the static magnetic field B0 is inclined to the vertical direction in space, which is defined by the direction of gravity, by the magic angle Θm≈54.74°A sample 30 in the form of a submillimeter-sized particle is trapped at a sample location inside the room temperature bore of the magnet device 10 by interaction of the sample 30 with an electromagnetic field in the form of a focused trapping laser beam. This kind of particle trap is known as a “single-beam gradient force trap” or more colloquially as “optical tweezers”. Optical tweezers have been known for a long time, based on work by Arthur Ashkin and colleagues dating back to the 1970s. The focused laser beam provides a three-dimensional confining potential for the sample around the focus of the laser beam. The confining potential is able to counteract the force of gravity, thereby enabling levitation of the sample simply by its interaction with the laser beam. The confining potential additionally also leads to trapping in the horizontal plane perpendicular to the direction of gravity.
The sample 30 is located in the “sweet spot” of the magnet device 10, i.e., in the region of greatest homogeneity of the static magnetic field B0 The sample 30 comprises at least one nuclear spin species, i.e., at least one species of nuclei with nonzero spin, By exposing the sample to the static magnetic field B0, a Zeeman splitting is induced for these spins, causing a spin polarization.
A resonance structure 40 is arranged in the room-temperature bore of the magnet device in immediate vicinity to the sample location, in the present embodiment, the resonance structure 40 comprises a flat carrier in the form of a printed circuit board (PCB). The PCB defines a carrier plane. The carrier plane is oriented vertically in space, Conductors are formed on the PCB, the conductors forming a printed excitation coil, Together with a capacitance, the excitation coil forms an LC resonance circuit. By providing radiofrequency (rf) power to the LC resonance circuit, an oscillating magnetic field (the so-called B1 field) can be created in the vicinity of the excitation coil. The B1 field is transverse to the direction z of the static magnetic field B0 i.e., it has a component that is perpendicular to the direction z. In
The resonance circuit is connected to a duplexer 43, which in turn is connected to a transmitter 41 and a receiver 42. The transmitter 41 is configured to provide pulsed if power to the resonance circuit to manipulate spin states of the nuclei in sample 30. The receiver 42 is configured to detect an electromotive force (EMF) that is induced in the resonance circuit due to a response of the nuclear spins to the rf pulses. The duplexer 43 ensures that the strong rf pulses from the transmitter 41 are directed to the resonance circuit while being blocked from the receiver 42, while the weak response signal received from the resonance circuit is directed to the receiver 42. The functionality of the duplexer may also be integrated into the resonance circuit, thus obviating the need of a separate duplexer.
The setup of the laser system of the first embodiment is adapted from [Monteiro2018]. In brief, a trapping laser beam 29 is created by a first laser 21 (the “trapping laser”). The trapping beam 29 is passed through an acousto-optic modulator (AOM) 22 for controlling beam power and through an electro-optic modulator (EOM) 23 for controlling the polarization of the beam. The trapping bear 29 is then reflected by a piezo-controlled mirror 24 for controlling the position of the beam. After passing through a first non-polarizing harmonic beam splitter 52, the trapping beam 29 is reflected upwards into a vertical direction opposite to the direction of gravity by a mirror 25. The exact direction of the trapping beam can be fine adjusted by adjusting the orientation of the mirror 25. The trapping beam 29 is focused to a diffraction limited focal spot at the sample location by a first aspherical lens 26 (e.g., having a focal length of 25 mm) and is re-collimated above the sample location by a second aspherical lens. The beam is then redirected towards a non-polarizing second harmonic beam splitter 54 and collected in a beam block 27.
A second laser beam 50, which acts as a diagnostic beam, is created by a second laser 51 (the “diagnostic laser”). The diagnostic beam has a different wavelength than the trapping beam and has fixed linear polarization. For instance, the trapping beam may have a wavelength of 1064 nm, and the diagnostic beam may have a wavelength of 532 nm. The diagnostic beam 50 is coaligned with the trapping beam by the beam splitter 52 and passes through the sample location together with the trapping beam before being coupled out from the trapping beam by the beam splitter 53, from where it goes to a diagnostic sensor system 54. The diagnostic sensor system 54 may comprise a polarization-sensitive sensor (PSS) for detecting changes of the polarization state of the diagnostic beam by its interaction with the sample. Additionally, one or more lateral position sensors may be provided for determining lateral displacements of the sample from the nominal sample location. Reference is made to [Monteiro2018], where further details are provided.
The trapping beam 29 not only acts to trap the sample 30 at the sample location, but it also acts to spin the sample about a vertical sample spinning axis R by exerting a mechanical torque on the sample (in other words, by transferring angular momentum to the sample). To this end, the trapping beam is circularly polarized, By controlling the polarization direction (left handed vs. right handed) and the degree of polarization (ellipticity) of the trapping beam using the EOM 23, the spinning frequency of the sample 30 can be controlled.
For more details concerning the optical setup of the first embodiment and the mode of operation of the optical setup, reference is made to [Monteiro2018], the content of which is incorporated herein by reference in its entirety.
In Practice, as the Trapping Laser 21, a 2 W “Mephisto” Laser from Coherent May be Used. Suitable non-magnetic posts, mounts, mirrors, polarizing beam splitters, harmonic beam splitters, lenses and 2D lateral effect position sensors are commercially available, e.g., from Thorlabs. A position detection and feedback system in the form of a piezo-mirror, piezo-controller and position sensing detector is also commercially available from Thordabs.
The disk-shaped magnet cryostat 12 defines a liquid helium (LHe) bath in which the superconducting magnet 11 is immersed. The LHe bath is defined by an inner shell 13. The inner shell 13 is surrounded by an outer shell 15, A vacuum is present between the inner shell 13 and the outer shell 15.
The auxiliary cryostat 16 likewise comprises an inner shell 18 and an outer shell 19. The inner shell 18 delimits a LHe reservoir that is fluidically connected with the LHe bath in the magnet cryostat 12. Between the inner shell 18 and the outer shell 19 of the auxiliary cryostat, a liquid nitrogen (LN2) reservoir is provided, surrounding the LHe reservoir as a thermal shield.
A shielding portion of a radiation shield element 14 is arranged in the vacuum between the inner shell 13 and outer shell 15 of the magnet cryostat 12. A flange-like contact portion of the radiation shield element 14 extends into the LN2 reservoir of the auxiliary cryostat 16, Thereby, the radiation shield element 14 is cooled to a temperature close to the LN2 temperature of 77 K. In this manner, efficient thermal shielding is achieved for the LHe bath of the magnet cryostat with minimal installation space. The radiation shield element 14 may, e.g., be made out of 2 mm thick Cu (or alternatively Al) due to its high thermal conductivity. Both the magnet cryostat 12 and the auxiliary cryostat 15 may comprise additional insulation layers, in particular, made of so-called superinsulation materials, as it is well known in the art.
The superconducting magnet 11 may comprise two pancakes of a REBCO high-temperature superconducting (HTS) tape separated by a Cu disk, which is covered in insulating tape on one side to prevent pancake-to-pancake current jumps. Stainless steel tape is wound tightly around the respective double pancakes to keep them in place during operation. The ends of the stainless steel tape may be fixed to protruding stainless steel 316 (ss316) metal sheets.
Superconducting shim elements (not shown) inside the magnet cryostat 12 as well as room-temperature shim elements (not shown) in the bore of the magnet cryostat 12 may be provided for homogenizing the static magnetic field B0 at the sample location, as it is well known in the field of NMR.
The magnet cryostat 12 is sufficiently flat to allow the trapping beam 29 to vertically pass through its room-temperature bore without hitting the magnet cryostat 12 when the magnet cryostat is inclined to the vertical direction by the magic angle, as in
The inner shell 13, the outer shell 15 and the radiation shield element 14 may be designed to be non-concentric at room temperature to account for differential thermal contraction of these elements when they are cooled to their respective operating temperatures, thus minimizing deformations due to thermal contraction during operation.
As illustrated in
The vacuum chamber 60 encompasses the focusing optics (in particular, the aspherical lenses) and the sample. It is made of a non-magnetic steel like ss316(L). The geometry of the chamber may be a 2-armed cube. Of course, different shapes for the vacuum chamber can be chosen according to need.
The resonator structure 40 used in this variant is shown in
A vacuum chamber 60 is arranged in the bore of the magnet cryostat 12. The vacuum chamber 60 may by cylindrical, forming a cylindrical probe body. The cylindrical probe body has a cylinder axis, which coincides with the longitudinal axis of the bore. The outer diameter of the cylindrical probe body matches the inner diameter of the bore, being only slightly smaller than the latter, such that it is possible to insert the cylindrical probe body into the bore. Instead of a vacuum chamber, any other kind of probe body may be provided for housing the optical components inside and inserting these components into the bore as a unit.
A sample is trapped inside a vacuum chamber 60 by a vertical trapping beam 83, which propagates antiparallel to the direction of gravity and is focused to a diffraction-limited focal point by an aspherical lens 85 to create a three-dimensional trapping potential for the sample, similar to the first and second embodiments. The trapping beam 83 is coupled into the vacuum chamber 60 by an optical fiber 81 and is collimated to form a collimated beam in vacuum by a collimator 82.
Torque is exerted onto the sample by a separate sample spinning beam 73. At the sample location, the sample spinning beam 73 is oriented at the magic angle Θm relative to the static magnetic field direction z. To this end, the sample spinning beam 73 is reflected into the magic angle by a tilted mirror 74. The exact angle of the sample spinning beam 73 can be adjusted by adjusting the tilt angle of the mirror 74. The sample spinning beam is focused to the sample location by an aspherical lens 75. Like the trapping beam, also the sample spinning beam 73 is coupled into the vacuum chamber 60 by an optical fiber 71 and is collimated by a collimator 72, instead of using the tilted mirror 74, a bent optical fiber may be used to directly provide the sample spinning beam 73 at the magic angle.
As in the first and second embodiments, a resonator structure 40 (shown only symbolically in
As illustrated in
The sample may be brought to the sample location by suspending it in aqueous solution and spraying the suspension towards the sample location with a nebulizer. In other embodiments, the sample may be positioned below the sample location on a sample support plate, e.g., a glass slide, and the sample support plate may be vibrated to make the sample “jump” into the sample location, where it is trapped. This works particularly well for larger sample particles, Trapping in liquids can be achieved by placing a thin glass container filled with the sample suspension at the sample location.
There are multiple options concerning the choice of sample. For instance, polymer particles, NV center diamonds or silica particles may be used. The most crucial aspects to consider are (i) the stability of the sample during sample spinning; (ii) sample heating due to interaction of the sample with the electromagnetic field; and (iii) the number of EPR- or NMR-active spins that can be detected.
To date, the most stable trapping in vacuum has been achieved with silica spheres. Due to the limitations on NMR sensitivity, the spheres should be as large as possible. For instance, for a fully enriched 29SiO2 sphere with 100 μm diameter, a conventional NMR setup suffices to detect the nuclear spins.
Dynamic nuclear polarization (DNP) may be employed to enhance sensitivity. For instance, a silica sphere can be γ-irradiated, producing radical defects that can be used for cross polarization from electrons to 29Si.
As another example, polystyrene spheres may be used. Polystyrene comprises more than 1014, spins of 1H (and 13C if enriched) in a 30 μm sphere, readily allowing for direct detection on 1H, Detection on 1H provides fast recovery time and a large gyromagnetic ratio, Neglecting cross polarization and recovery time, detecting on 1H is 32 times more sensitive as compared to 13C and 57 times more sensitive compared to 25Si,
NV centers have been levitated in air successfully and provide a slightly higher amount of NMR-active nuclei than silica spheres for identical size. They are of considerable interest due to their potential as qubits and are being researched actively, DNP can be used to improve sensitivity. NV centers may also be investigated by EPR.
Pure nanodiamonds with 1000 times greater purity than NV centers have been levitated at low pressures without heating due to their low absorption at 1064 nm. For details see [Hoang2016]. Active center-of-mass feedback control may be used to stabilize the lateral positions of the nanodiamonds.
Vaterite has been levitated and rotated with similar conditions to silica and can be synthesized from reasonably cheap starting materials, which are available 13C enriched.
Since rotation of the sample averages out anisotropic interaction to first order, quadrupolar nuclei may be an attractive species to demonstrate how the NMR linewidth changes depending on the polarization of light, Ruby or Al2O3 spheres are one option, since 27Al is a 100% abundant spin 5/2 system with a similar gyromagnetic ratio as 13C.
Ruby is also an interesting system for studying directly detected or optically detected EPR of a rotating sample due to the presence of Cr3− impurities.
Borosilicate glass is about 90% transparent to 1064 nm and contains spin-3 10B and spin-3/2 11B nuclei, which may be detected directly or indirectly via dipolar coupling on the silicon atoms. Furthermore, γ-irradiation allows access to DNP methods.
If sample stability in vacuum is an issue, rotation in liquids is an alternative. For instance, gold nanorods have been proven to rotate at high frequencies (42 kHz in a colloidal suspension).
In some cases, it may not be possible to levitate the sample by the action of an electromagnetic field (e.g., by a laser beam) alone. In such cases, it may be required to add a sample support structure for aiding with support of the sample against the force of gravity.
In alternative embodiments, the sample 30 is both trapped and rotated by the laser beam 150, and the resonator is used for exciting and/or detecting EPR.
Many modifications of the arrangements of the sample spinning axis and the static magnetic field direction in space are possible. In particular, it is possible to spin the sample about a horizontal spinning axis, and to arrange the static magnetic field at the magic angle relative to the horizontal spinning axis. The presently proposed method of sample spinning is not only useful for spinning the sample at the magic angle. It is possible to spin the sample at other angles relative to the static field direction as well.
Instead of spinning (and possibly trapping) the sample using circularly polarized laser light in the UV, VIS or IR regions or using a microwave field, it is also possible to spin (and possibly trap) the sample using time-varying electric fields, as in a Paul trap. For instance, the electrical field on poles within a stator could be set to oscillate at the spinning frequency to provide torque. Torque could also be created by linear momentum transfer from photons that hit the spinning sample off-center to result in translational to angular momentum transfer.
It is also possible to use different kinds of electromagnetic fields for trapping and spinning. For instance, a Paul trap may be used for trapping the sample, while circularly polarized light may be used for applying torque to the sample, With this combination, comparatively large particles may be trapped and spun, the particle diameter even exceeding 1 mm,
It is also possible to first spin the sample by a known mechanical spinning method, e.g., by the action of a fluid, and use the electromagnetic sample spinning field only to further accelerate and/or maintain the thus-induced spinning motion of the sample.
The presently proposed method of sample spinning may be combined with any known method of polarization enhancement in EPR and NMR, in particular, with optically pumped EPR or NMR or dynamic nuclear polarization (DNP) methods Such methods are well established.
The presently proposed method of sample spinning may also be combined with any known method of spin manipulation in EPR and NMR, in particular, with multiple-pulse methods, cross-polarization, homo- and heteronuclear decoupling etc. Many such methods have been developed over the decades.
Finally, the presently proposed method of sample spinning may be combined with any known detection method for detecting a response of the spins in the sample to the spin manipulation, in particular, detection of an EMF induced in an inductor, changes of resonant properties of a resonator, and optical detection.
The resonance structure for manipulating the spin state of the sample (and optionally for detecting its response) may have any known design that does not interfere with the sample spinning field. In particular, instead of using a printed coil on a carrier like a PCB or semiconductor chip, a traditional solenoid microcoil or Helmholtz microcoil may be used. The microcoil may be designed with a gap to allow a laser beam to pass through the gap unhindered.
Number | Date | Country | Kind |
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22151713.9 | Jan 2022 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2023/050740 | 1/13/2023 | WO |