Field-frequency locked X-band Overhauser effect spectrometer #DNPNMR
 

From The DNP-NMR Blog:

Field-frequency locked X-band Overhauser effect spectrometer #DNPNMR

This article is already a bit older. However, it nicely illustrates that DNP, specifically ODNP has been around for a while already, and gives some interesting specifics on the instrumentation that are still valid today.


Chandrakumar, N. and P.T. Narasimhan, Field-frequency locked X-band Overhauser effect spectrometer. Review of Scientific Instruments, 1981. 52(4): p. 533-538.


http://dx.doi.org/10.1063/1.1136634


The design and construction of an Overhauser Effect Spectrometer operating at X band is described. The ESR section is a Varian V-4502 spectrometer equipped with a 9-in. electromagnet and a shim coil assembly. NMR detection is based on a broadband rf hybrid juction feeding a coil in an X-band quartz dielectric cavity. Signal processing is carried out at a constant intermediate frequency of 25.1 MHz with a Varian V -4311 fixed frequency rf unit. The mixing scheme employed to translate the NMR information to 25.1 MHz is described. Medium resolution performance (resolution _10-6 ) for the NMR is achieved under field-frequency locked conditions. The lock is based on a Super-Regenerative Oscillator (SRO) housing a control sample, and operating as a field-tracking frequency source. This SRO injects into an oscillator which excites the analytical sample resonance and also serves as a local oscillator, thereby making the locked spectrometer multinuclear in capability. Typical Overhauser effect recordings of protons and fluorines are presented.


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