Inelastic neutron scattering (INS) studies on low frequency vibrations of 1,4-benzoquinone

Inelastic neutron scattering (INS) infrared (IR) and Raman (R) spectra in the region below 1700 cm−1 of solid 1,4-benzoquinone (p-BQ) are compared with calculated frequencies and intensities for the gas phase. In the case of INS spectra a very good agreement is found when the frequency scaling factor markedly higher than unity (1.05) is assumed. This is most probably due to the fact that in the solid state all hydrogen and oxygen atoms are involved in the C–H⋯O hydrogen bond formation. The internal dynamics of p-BQ molecules reflected in the low frequency region is to a marked extent affected by these interactions. The environment effect is best reflected in the INS spectra recorded at 22 K. The complementarity of INS, IR and R spectra, appearance of overtones and summation modes and overlapping of closely located bands are discussed.