Abstract:
Experimental and theoretical investigations were made of the dependence of the amplitude of an optoacoustic signal on the radius of a region excited by a focused beam. A linearized equation for the pressure was solved to show that the acoustic signal profile was governed primarily by the beam radius and that for r0 < cτ (r0 is the beam radius, τ is the heat evolution time, and c is the velocity of sound) the amplitude rises as r03/2, whereas for r0 > cτ it is proportional to r01/2. A series of experiments was carried out on the absorption in ozone and these experiments confirmed the r03/2 dependence for r0 < cτ.