arXiv subjects

Enrico Ravera

Publications and source records attributed to Enrico Ravera.

3 recordsLinked to original sources

arXiv2021

Phase distortion-free paramagnetic NMR spectra

The NMR spectra of paramagnetic substances can feature shifts over thousands of ppm. In high magnetic field instruments, this corresponds to extreme offsets, which make it challenging or impossible to achieve uniform excitation without phase distortion. Furthermore, because of the intrinsic presence of a dead time during which spins freely evolve, a further phase distortion occurs. A decade ago, a processing approach based on the analysis of the statistics of the phase of the spectrum was proposed to denoise NMR spectra. In this manuscript it is demonstrated that this approach is applicable to obtain paramagnetic NMR spectra that are free of phase distortion, even though the quantitative information of peaks intensities is lost. This is demonstrated on the high field spectra of a prototypical nickel(II)-complex and through the analysis of simulated data.

physics.chem-ph↗

arXiv2019

Biomolecular NMR at 1.2 GHz

The development of new superconducting ceramic materials, which maintain the superconductivity at very intense magnetic fields, has prompted the development of a new generation of highly homogeneous high field magnets that has trespassed the magnetic field attainable with the previous generation of instruments. But how can biomolecular NMR benefit from this? In this work, we review a few of the notable applications that, we expect, will be blooming thanks to this newly available technology.

physics.chem-ph↗

arXiv2019

Pseudocontact shifts and paramagnetic susceptibility in semiempirical and quantum chemistry theories

Pseudocontact shifts are traditionally described as a function of the anisotropy of the paramagnetic susceptibility tensor, according to the semiempirical theory mainly developed by Kurland and McGarvey (R.J. Kurland and B.R. McGarvey, J. Magn. Reson. 2, 286 (1970)). The paramagnetic susceptibility tensor is required to be symmetric. Applying point-dipole approximation to the quantum chemistry theory of hyperfine shift, pseudocontact shifts are found to scale with a non-symmetric tensor that differs by a factor g/ge from the paramagnetic susceptibility tensor derived within the semiempirical framework. We analyze the foundations of the Kurland-McGarvey pseudocontact shift expression and recall that it is inherently based on the Russell-Saunders (LS) coupling approximation for the spin-orbit coupling. We show that the difference between the semiempirical and quantum chemistry pseudocontact shift expressions arises directly from the different treatment of the orbital contribution to the hyperfine coupling.

physics.chem-ph↗