# What is the experimental evidence for quantization of lattice vibrations?

Is there any direct experiment to show the quantization of lattice vibrations?

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Does a measurement of the low-temperature heat capacity of a crystalline solid not count as direct experimental evidence? –  Mark Mitchison Sep 20 '13 at 16:23

Lattice vibration excitations, i.e. phonons, are typically at energies of $\sim 25 meV$ which corresponds to room temperature. Therefore, neutron scattering with thermal neutrons is done. Thermal neutrons are neutrons from a nuclear power plant which are moderated to room temperature by sending them through a big tank of water, so they also have energies on the oder of $25meV$. Also, the de Broglie wavelength of neutrons is about 1 angstrom=$10^{-10}m$, so that neutrons are capable of resolving interaction motion.