Abstract
Recently there has been an increased interest to apply the sensitive β-decay asymmetry detected nuclear magnetic resonance (β-NMR) technique to biological studies. A liquid-sample β-NMR setup was build at ISOLDE to allow such investigations and to use the resolution gain of liquid-state NMR in nuclear physics. As part of this setup a magnetic field locking system, a set of printed circuit board shimming coils, a sample exchange system, a set of compact β-detectors and a custom experimental vacuum chamber were developed. The main magnetic field was stabilized down to the ppm level by the locking system while allowing the direct determination of the absolute magnetic field. The homogeneity of the magnetic field was improved to ≤ 5 ppm over the sample volume by the shimming coils. Time spent on changing samples was reduced by a factor of five by the liquid sample exchange system. During experiments it was possible to continuously observe the liquid sample thanks to the custom chamber and compact β-detectors. The absolute field determination allows for a novel way to reference β-NMR measurements, removing the need for time consuming reference measurements. The improved accuracy and resolution resulting from these innovations allows the study of the distribution of nuclear magnetization and (bio)chemicals using high-accuracy liquid-sample β-NMR.
Highlights
The emission of β-radiation from an ensemble of oriented nuclei can exhibit a high degree of September 30, 2021 asymmetry
The β-asymmetry that is observed in βdecay asymmetry detected nuclear magnetic resonance (NMR) (β-NMR) experiments, scales linearly with the nuclear polarisation[2], i.e. the amount of first order nuclear orientation within an ensemble
A stable B0 is essential for β-NMR experiments, especially those performed in liquid samples, where chemical shifts of a few ppm are often measured[22]
Summary
The emission of β-radiation from an ensemble of oriented nuclei can exhibit a high degree of September 30, 2021 asymmetry. This was first observed by Wu et al, with a low temperature spin-oriented sample of 60Co nuclei proving that the weak force does not conserve parity[1]. Due to the magnitude of the observed asymmetry compared to other types of anisotropically emitted radiation, this effect is a promising probe for several nuclear effects[2] It can be used as a very sensitive means of detecting nuclear magnetic resonance (NMR) signals, which can be up to ten orders of magnitude more sensitive when compared to conventional NMR on stable isotopes[3] as it allows one to measure signals from as few as 107 nuclei. The high level of polarisation of the ensemble of nuclei is one of the reasons for the high sensitivity of the technique, the other being the detection by β-radiation
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