Photoacoustic method for the measurement of the nonlinearity parameter of liquids

A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.