VIBRATIONAL BEHAVIOR OF AMORPHOUS AND CRYSTALLINE ETHYLBENZENE

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.