Исследование ЯМР-сигналов рубидия в водных растворах и определение магнитных моментов ядер Rb-85 и Rb-87

Abstract

Study of NMR signals of rubidium in aqueous solutions and determination of the magnetic moments of Rb-85 and Rb-87 nuclei Yuriy Ilyich Neronov, Anton Nikolaevich Pronin All-Russian Research Institute of Metrology named after V.I. D. I. Mendeleeva, St. Petersburg, Russia, yineronov@mail.ru, and a.n.pronin@vniim.ru Annotation. The problem of increasing the accuracy of determining the magnetic moments of rubidium-85 and rubidium-87 nuclei based on the study of NMR signals of RbNO3 and RbCl solutions in water is considered. The spectral linewidth of the NMR signals from the 85Rb and 87Rb nuclei is a hundred times greater than the similar width of the signals from the nuclei for other neighboring alkaline elements of the periodic table, and such a broadening limits the possibilities for precision registration of nuclear resonance frequencies. Simultaneous registration of nuclear magnetic resonance signals from water protons and from rubidium nuclei was used in the work, which makes it possible to minimize the spread of data for the resonance frequency ratio. The ratios of the resonance frequencies of water protons and 85Rb, 87Rb nuclei were determined for aqueous solutions of RbCl and RbNO3 with concentrations from 0.5 to 2.0 mol/kg H2O. As a result, the ratios of magnetic moments (87Rb)/(85Rb) = 2.0333981(2) were calculated with a relative uncertainty d ≈ 10-7. The data on the resonance frequency ratio f(1H)/f(87Rb) for the content of rubidium salts in water were extrapolated to zero concentrations and f(1H)/f(87Rb) = 3.0561795(2) was determined for rubidium ions surrounded by water molecules . As a result, the magnetic moments are determined (85Rb)=1.353067(37); (87Rb)=2.751324(74). The obtained results are compared with the data of previous works. Annotation. The problem of increasing the accuracy of determining the magnetic moments of rubidium-85 and rubidium-87 nuclei based on the study of NMR signals of RbNO3 and RbCl solutions in water is considered. The spectral linewidth of the NMR signals from the 85Rb and 87Rb nuclei is a hundred times greater than the similar width of the signals from the nuclei for other neighboring alkaline elements of the periodic table, and such a broadening limits the possibilities for precision registration of nuclear resonance frequencies. Simultaneous registration of nuclear magnetic resonance signals from water protons and from rubidium nuclei was used in the work, which makes it possible to minimize the spread of data for the resonance frequency ratio. The ratios of the resonance frequencies of water protons and 85Rb, 87Rb nuclei were determined for aqueous solutions of RbCl and RbNO3 with concentrations from 0.5 to 2.0 mol/kg H2O. As a result, the ratios of magnetic moments (87Rb)/(85Rb) = 2.0333981(2) were calculated with a relative uncertainty d ≈ 10-7. The data on the resonance frequency ratio f(1H)/f(87Rb) for the content of rubidium salts in water were extrapolated to zero concentrations and f(1H)/f(87Rb) = 3.0561795(2) was determined for rubidium ions surrounded by water molecules . As a result, the magnetic moments are determined (85Rb)=1.353067(37); (87Rb)=2.751324(74). The obtained results are compared with the data of previous works. Keywords: precision determination of nuclear magnetic moments, simultaneous registration of NMR signals from two types of nuclei, quantum radiophysics