Abstract
The vibrational excitations of crystalline solids corresponding to acoustic or optic one-phonon modes appear as sharp features in measurements such as neutron spectroscopy. In contrast, many-phonon excitations generally produce a complicated, weak and featureless response. Here we present time-of-flight neutron scattering measurements for the binary solid uranium nitride, showing well-defined, equally spaced, high-energy vibrational modes in addition to the usual phonons. The spectrum is that of a single atom, isotropic quantum harmonic oscillator and characterizes independent motions of light nitrogen atoms, each found in an octahedral cage of heavy uranium atoms. This is an unexpected and beautiful experimental realization of one of the fundamental, exactly solvable problems in quantum mechanics. There are also practical implications, as the oscillator modes must be accounted for in the design of generation IV nuclear reactors that plan to use uranium nitride as a fuel.
| Original language | English |
|---|---|
| Article number | 1124 |
| Journal | Nature Communications |
| Volume | 3 |
| DOIs | |
| State | Published - 2012 |
Funding
We acknowledge A.I. Kolesnikov, J. Carpenter, E. Iverson and R.J. McQueeney for useful discussions, and A.T. Savici, T.E. Sherline and M.J. Loguillo for technical support. This research was supported by the US Department of Energy, Office of Basic Energy Sciences. A.A.A., G.E.G., G.J.M., D.L.A. and S.E.N. were supported by the Scientific User Facilities Division. G.D.S. and G.M.S. were supported by the Center for Defect Physics and Energy Frontier Research Center. Experiments were performed at the Spallation Neutron Source, which is sponsored by the Scientific User Facilities Division.