A Gardener's Year (Cambridge Library Collection - History)

Liketheearthitself,thenucleusofanatomfrequentlyrotatesaboutanaxis.Undertheinfluenceofamagneticfieldtheaxisofrotationitselfrotates.Therateofthis'precessional'motionisproportionaltothestrengthofthemagneticfieldandusuallyliesintheregionofradio-frequencies.Ifacollectionofsuchnucleiisplacedinamagneticfieldissubjectedtoradiowavesatexactlythefrequencyofprecession,thereisaresonanceeffect,whichcanbeusedtomeasurethefrequencyoftheprecession.Thiseffectiscallednuclearmagneticresonance.Thesubjectconcernsallphysicists,particularlynuclearphysicistsandthoseinterestedinthesolidstate.Itisofgrowingimportancetochemists,metallurgistsandelectricalengineersandtherehavebeensomebiologicalandgeophysicalapplications.Nuclearmagneticresonancehasalreadyfoundconsiderableusesintheoilindustry,inindustriesconnectedwithmagnetconstruction,isotopeextraction,plasticsandrubber.