Assignment of tunnelling lines by single crystal neutron spectroscopy

摘要: Abstract By rotating a small single crystal of tribromomesitylene around the ω axis, three tunnelling lines, one due to each methyl groups in molecule, vary sinusoidally intensity with phase differences 60°. An assignment modes can therefore be made directly. Similar measurements librational principle also allow such an but practice not so clearly because presence lattice modes. We believe this is first time that excitations equal numbers chemically equivalent crystallographically inequivalent have been experimentally assigned.