Neutron triple-axis and time-of-flight experiments on ethylbenzene are
presented. We have investigated selectively deuterated, amorphous and
crystalline ethylbenzene in the frequency range up to 100 meV. Wherea
s vibrational excitations above 50 meV are not influenced by the local
disorder, we find clear changes for the methyl group libration mode a
nd other side-chain librations. The most pronounced feature is the pre
sence of the Boson peak in the amorphous sample below 5 meV, which can
not be explained by a broadening of modes.