Acoustic properties of gas bubbles coated with monolayers of oil substance1

A gas bubble coated with a monolayer of oil substance, submerged in liquid, in the field
of an acoustic wave is given theoretical consideration in this paper. Radial oscillations in the
wave frequency band much below the resonance frequency depend mainly on the value of
the monolayers modulus of elasticity and relaxation time t~ of the process of molecule
reorientation which occurs in the monolayer due to its deformation. The following
parameters were calculated: shift of the resonance frequency, damping constant of radial
oscillations, and acoustic wave scattering and extinction cross-sections for a gas bubble in
water, coated with a condensed monolayer of Extra 15 engine oil in angular frequency range
roe [101 ~ 10'] rads - I and range of radii of bubbles (3- SO) ).lm. Predicted values of the
damping constant and extinction cross-section in the wave frequency range ro < a(a = 2rr./1,)
are by several orders of magnitude greater than those for a bubble with a clean su rface. This
effect is especially distinct in the case of microbubbles (with ~m radii and smaller) placed at
small depths (up to about 0.5 m).