Transformation of the diffraction patterns of screens into the diffraction patterns of additional screens in the course of scattering by a gas perturbation or by a particle in a laser beam caustic

The spatial distribution of the scattered-radiation energy during focusing, in atmospheric air, of the fourth-harmonic beam of a pulsed neodymium laser (λ = 264 nm) with an annular cross section was studied experimentally. Shortening of the UV scattered-radiation by a factor of 2 — 5, compared with the duration of the laser pulse, was observed. An interference structure of the scattered radiation, varying with increase in the laser-pulse energy, was recorded. The diffraction rings and bands originating from screens were transformed into analogous diffraction rings and bands from additional screens. This can be accounted for by the scattering of the laser beam on a gas perturbation or on a particle in the caustic. Experiments were performed on the scattering of radiation with λ = 0.63 μm on formations with an abrupt boundary, which confirmed the above hypothesis.