A study on vibrational relaxation of liquid halogenated benzenes by Brillouin scattering

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Brillouin spectra of four liquid halogenated benzenes (C 6 H 5 F, C 6 H 5 Cl, C 6 H 5 Br, C 6 H 5 I) have been investigated at scattering angles from 60 degrees to 150 degrees at temperatures from 20 degrees C to 30 degrees C, and the velocity dispersion in the gigahertz region has been obtained. The data have been analysed for a single relaxational behaviour with the ultrasonic velocity at 5 MHz, and the relaxational frequency and strength have been evaluated. Agreement between the experimental and theoretical relaxational strength has been achieved by assigning the relaxation to molecular vibrational relaxation.