Photoacoustic waves and corresponding diffraction rings pattern have been observed in an organic liquids (6- amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c] pyrazoles) and studied using different optical experiments. Structure vibrations relative to Raman scattering propagates ultrasonic waves in the solution and performs pressure waves that lead to a refractive grating in the molecular solution. The induced photoacoustic grating diffracts the incident laser beam. High dense diffraction ring pattern are observed that couldn't be interpreted with previous mechanisms such as high nonlinear refractive index. This phenomenon is a kind of stimulated Raman scattering that leads to circular diffraction of the laser beam. Z-scan and optical photoacoustic z-scan (OPAZ-scan) experiments are applied to study nonlinear optical responses. This phenomenon could propose new photo-acoustic sensors based on diffraction pattern of the incident beam
