Low‐frequency molecular vibrations in solid n ‐paraffins by neutron inelastic scattering: n ‐Pentane, n ‐hexane, n ‐heptane, and n ‐octane

摘要: The torsional and skeletal bending fundamentals in solid n ‐pentane, ‐hexane, ‐heptane, ‐octane are measured by the method of cold neutron inelastic scattering. For this series ‐paraffins, maximum frequencies torsion modes approach 190 500 cm−1, respectively, agreement with previous measurements on polyethylene. average frequency two end‐methyl torsions is found to be 240 cm−1. A normal coordinate analysis, performed using only intramolecular valence force fields for each molecule, used as a guide spectral assignments. These results compared theoretical dispersion curves polyethylene, without intermolecular forces. Chain‐end effects appear little significance these low‐frequency modes, even chain lengths short seven or eight carbons.