Ultrasonic and Light-Scattering Studies of Benzene

A detailed examination of ordinary Brillouin light scattering in liquid benzene at 25°C reveals that no single total relaxation of all the vibrational modes can make the ultrasonic absorption data consistent with the light-scattering data. Consistency can be achieved, however, by assigning a viscosity η1 = 0.845P and a relaxation time >τ1″ = 2.98 × 10−10sec(f1″ = 533 MHz) to all the vibrational modes except the lowest; and η2 = 0.07P with τ2″ = 3.6 × 10−11sec(f2″ = 4400 MHz) to the degenerate lowest mode. The volume viscosity ηυ is equated to 43ηs and ηυ + 43ηs is made a relaxing viscosity η3 with τ3″ = 10−12sec.