The Bordoni maximum and the Peierls energy: Lecture on receiving the Zener medal

Acoustic spectroscopy and electrical resistivity measurements have been employed to investigate the two relaxation processes occurring at liquid He temperature in very dilute Y–H and Sc–H alloys, and ascribed to H tunnelling systems near single or paired O traps. At very low H concentration, the peak due to the O–H tunnelling system becomes extremely narrow and is describable in terms of incoherent tunnelling with phonon assisted transitions.