Some Details about our NMR Instruments

Magnets, Consoles, Probes 

The four different spectrometers of our group allow all kind of NMR experiments ranging from basic wide line solid-state NMR measurements to highly sophisticated tailored NMR methods probing molecular properties at the interplay of different phases and environments.  

300 MHz Wide Bore NMR Spectrometer

The 300 MHz wide-bore NMR spectrometer is our working horse for solid-state NMR routine applications like CP-MAS and static deuterium NMR: wide lines, low resolution, large sample quantities.   more

500 MHz Wide-Bore NMR Spectrometer

The 500 MHz wide-bore NMR spectrometer covers basically all typical solid-state NMR applications and is optimized for temperature dependent MAS NMR measurements from -50°C up to 250°C.  more

700 MHz Standard-Bore NMR Spectrometer

The 700 MHz standard-bore NMR spectrometer is a solid-state NMR spectrometer allowing as well for high-resolution solution applications. It combines feautres of high-reolution spectrometers like fiel lock and gradient amplifiers, with high power amplifiers and fast MAS NMR equipment with up to 65 kHz MAS spinning frequency of solid-state NMR spectrometers.  more

The 850 MHz High-Field NMR Spectrometer

The 850 MHz high-field NMR spectrometer covers all advanced solid-state NMR, high-resolution-MAS NMR and solution NMR. For most applications, state of the art equipment is available and switching the spectrometer between the different applications takes less than 30 min.  more

The 300 MHz Wide-Bore Solid-State NMR Spectrometer

Our smalles and oldest NMR spectrometer is the 300 MHz solid-state NMR spectrometer. An Oxford Instruments/Spectrospin wide bore NMR magnet from 1986 is operated by a digital two channel  Bruker Avance II solid-state NMR console with high power rf amplifiers (1 kW ¹H, 1 kW X) but without lock and gradient amplifiers. A broad range of commercial as well as home build NMR probes for special applications is available for this spectrometer.

The spectrometer is used for routine direct excitation and CP-MAS NMR applications on ¹³C and ²⁹Si, which typically do not provide better spectral resolution at higher static magnetic field strength, as the spectral resolution is in most cases determined by the molecular disorder due to irregular packing in the sample material. Other typical applications are static ²H NMR measurements, where higher field strength will improve only signal to noise of the NMR spectra but has again no influence on the spectral reslution. Due to it’s very robust and esay to fix hardware, it is as well our solid-state NMR training spectrometer

The most used NMR probes are Bruker 4 mm VTN-MAS ¹H-X (high range/low range),  7 mm VTN-MAS ¹H-X and a home build static ²H NMR probe. Many more commercial and home build probes are available.

The 500 MHz wide-bore solid-state NMR spectrometer

The 500 MHz wide-bore NMR system is our working horse system of the solid-state NMR group. The 500 MHz wide-bore Magnet, manufactured by Oxford Instruments / Spectrospin in 1992, is operated by a Bruker Avance III console with 4 high-power rf-channels (¹H / ¹⁹F / X / Y ) . Experimental conditions for the NMR measurements are adjusted with a Bruker MAS II controller for MAS NMR experiment, a BSVT temperature controller and a Bruker BCU II chiller for variable temperature (MAS) NMR measurements in the temperature range from -50°C up to 250°C. The spectrometer is equipped with a broad range of static and MAS NMR probes for variing sample diameter, allowing for almost all kinds of solid-state NMR measurements common in material science.

Typical NMR measurements performed at this spectrometer are variable temperature MAS- and CP-MAS NMR experiments, monitoring dynamic processes in all kinds of materials and samples on the molecular level. At 25 kHz MAS spinning frequency, the spectrometer provids some spectral resolution on protons, which can further be improved via two dimensional CP-MAS correlation experiments using the typically better resolution on hetero-nuclei in most samples.

The 2.5 mm ¹H/¹⁹F/X MAS NMR probe provides the unique possibility to correlate ¹H signals with ¹⁹F signals and other hetero-nuclei like ¹³C, ³¹P or ²⁹Si at MAS spinning frequencies up to 30 kHz. The moderate field strength of 500 MHz proves ideal for the observation of ¹⁹F MAS spectra and in partucular for ¹⁹F double-quantum NMR correlation spectra, as the spread of signals is still smaller than the spinning frequency and excitation problems due to field dependend chemical anisotropy are still limited.

The 700 MHz standard-bore NMR spectrometer

The core of the 700 MHz solid-state NMR spectrometer is an ultra-shielded 16.4 T standard-bore (54mm bore diameter) superconducting NMR magnet. The spectrometer is operated by a 4 channel Bruker Avance III console with field lock and gradient amplifier for solution and and high-power rf amplifiers for solids applications. For the spectrometer high-resolution NMR probes as well as fast MAS NMR probes controlled by a MAS II controller are available. The sample temperature is adjusted via a Bruker BSVT temperature controller combined with a Bruker BCU II chiller allowing for solution NMR measurements in a temperature range from -50°C to 150°C and variable temperature MAS NMR measurements in the range from -20°C to 110°C depending on the MAS spinning speed and the used MAS probe.

Most high resolution NMR measurements at this spectrometer are performed using a ¹H/¹³C/¹⁵N triple resonance inverse (TXI) probe with gradients, field lock and automated rf adjustment (ATMA) or a broad band inverse probe (BBFO) with field lock and pulsed gradient, where rf tuniring on 1H and X channel as well as impedance match have to be done manually. 

For the MAS NMR measurements, 2.5mm ¹H/X MAS NMR probes are commonly used for VT-MAS NMR experiments at MAS spinning frequencies typically at 25 kHz in a temperature range from -20°C to 110°C. Here, a spinning speed depended calibration of the sample temperature is essential for the success of the experiments and the physico-chemical interpretation of the temperature depence. The ¹H spectral reslution can be improved, using the 1.3mm ¹H/X MAS NMR probe offering MAS spinning frequencies up to 65 kHz. 1H X correlation spectra, however, at these MAS spinning frequencies and low sample quantities are very challening and the measurements are limited to a narrow temperure range ( 20°C - 60°C).

The 850 MHz high-field NMR spectrometer

The 20T standard bore NMR magnet is the high-light of our NMR system. It is a pumped superconducting magnet system cooling the field coil in a superfluid 2 K (-271°C) helium bath in order to generate the extremely stable 20T magnetic field with a constant almost 300A superconducting current. The spectrometer is operated with a 4 channel Bruker Avance NEO console equipped gradient amplifier and field lock and sample changer for high-resolution NMR measurement and high power amplifiers and a Bruker MAS III controler for solid-state NMR applications.   

The 850 MHz high-field NMR spectrometer is a real hybrid spectrometer, where setups for high-resolution NMR measurments with a sample changes, high-resolution MAS NMR for NMR studies of gels and assembling system and last but not least MAS NMR equippment for solids mit MAS spinning speeds up to 65 kHz. The switchng between the different setups is done routinely and takes less than 30 min. For all setups a Bruker BSVT temperature controller with Bruker BCU II chiller to adjust the sample temperature.