The incident Gaussian beam is expanded with spherical harmonics function and the beam factors of Gaussian beam are calculated using the finite series methods. The analytical expression of scattering form function is deduced according to the theory of acoustic scattering for spherical particles lies off the axis of Gaussian beam. The effects of the beam waist of the Gaussian beam and the distance from the Gaussian beam center on the characteristics of acoustic scattering are investigated. Using numerical simulations, the scattering patterns of rigid spherical particles in the Gaussian beam are obtained for different conditions.Our results show that: the amplitude of scattering form function gradually increases with the width of beam, and when the beam waist is 20 times the wavelength, the scattering form function is consistent with plane wave exactly. The amplitude of scattering form function gradually decreases with the particles off-axis distance and angle.Our results provide a theoretical basis for the particle manipulation relied on focused beam.

Gaussian beam; spherical particles; scattering property; beam width