Relativistic, QED, and nuclear mass effects in the magnetic shielding of H3e

Abstract

The magnetic shielding of 3 He is studied. The complete relativistic corrections of order O͑␣ 2 ͒, leading QED corrections of order O͑␣ 3 ln ␣͒, and finite nuclear mass effects of order O͑m / m N ͒ are calculated with high numerical precision. The resulting theoretical predictions for = 59.967 43͑10͒ ϫ 10 −6 are the most accurate to date among all elements and support the use of 3 He as a NMR standard.

13C shielding scale for MAS NMR spectroscopy

“…• The identical set of NMR tubes was also used for the measurements of 13 C resonance frequencies of the three selected reference samples, the results were as follows: ν C (pure liquid TMS) = 125.8774166 MHz, ν C (1% of TMS in CDCl 3 ) = 125.8775106 MHz and ν C (solid C 60 ) = 125.8955126 MHz; • The 13 C shielding constants of reference samples were determined from the magnetic moments of 3 He and 13 C bare nuclei (µ He = −2.127625306µ N [6,15] and µ C = 0.70236944(68)µ N [8,16] ) and the shielding of an isolated helium-3 atom (σ He = 59.96743 ppm [9] ) according to the equation:…”

“…The main reference sample was prepared by sealing a small amount of helium-3 from the calibrated part of vacuum line in a micro spherical ampoule (Wilmad 529-A). The concentration of helium-3 in the reference sample was 0.042 mol·l −1 and the value of 59.96743 ppm [9] was adopted as its nuclear magnetic shielding (all intermolecular effects in 3 He shielding were neglected on the basis of our previous observation of helium-3 shielding in the gas phase [10] and Antušek et al theoretical studies [11] ). Other compounds like pure TMS, 1% TMS in CDCl 3 and solid fullerene (C 60 ) were degased and also sealed in the Wilmad 529-A ampoules.…”

A Brief Review on Bioactive Compounds from Species

“…According to the IUPAC conventions [11] Recently we have demonstrated a new method of 1 H and 13 C shielding measurements available for isotropic species on any standard nuclear MR spectrometer [7]. It is based on the magnetic shielding in an isolated helium-3 atom ( 3 He = 59.96743 ppm) [6], on our investigation of resonance frequency for the same atomic object [12] and the determination of unknown shielding according to Eq. (6):…”

“…It is based on the calculated value of shielding in an isolated helium-3 atom [6] and our own observation of resonance frequencies in a constant magnetic field [7]. As shown, the chemical shifts can be successfully replaced by the shielding parameters for numerous nuclei, which was not possible in nuclear MR spectroscopy before.…”

The Radiofrequency NMR Spectra of Lithium Salts in Water; Reevaluation of Nuclear Magnetic Moments for 6Li and 7Li Nuclei

“…A crucial role in the estimations of lithium nuclear magnetic moments has been played by knowledge of the diamagnetic corrections for helium atoms and lithium cations. As the reference point of helium measurements was chosen very precise shielding value of single atom nuclei σ 0 ( 3 He) = 59.96743(10) ppm calculated with relativistic corrections, QED (Quantum Electrodynamics) corrections and nuclear mass effects [19]. At the beginning, we measured the 3 He NMR signal against that of gaseous systems; the difference is 2.7675(25) ppm in the chemical shift category, independently on the concentration of helium in water.…”