McConnell equation describes the proportional dependence of the hyperfine splitting constant

Hyperfine structure

The term hyperfine structure refers to a collection of different effects leading to small shifts and splittings in the energy levels of atoms, molecules and ions. The name is a reference to the fine structure which results from the interaction between the magnetic moments associated with electron...

  on the spin density (the probability of an unpaired electron being on a particular atom) in aromatic radical compounds such as benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

 radical anion .



is an empirical constant equal to 2.25 mT.

History

The equation is named after Harden M. McConnell

Harden M. McConnell

Harden M. McConnell is an American physical chemist at Stanford University.-Birth and education:Harden M. McConnell was born on July 18, 1927 in Richmond, Virginia. He completed his Bachelor of Science from George Washington University in 1947 and his PhD from the California Institute of...

 of Stanford University

Stanford University

The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

, who first presented it in 1956 in an article in the Journal of Chemical Physics

Journal of Chemical Physics

The Journal of Chemical Physics is a scientific journal that publishes research papers on all areas of chemical physics. Two volumes, each of 24 issues, are published per year. It is published by the American Institute of Physics. The editors have been:...

.