Low-pressure differential mobility analysis was used to study the aerosol formed during 1064-nm pulsed Nd3+ :YAG laser ablation of a solid cesium iodide (CsI) target. Measurements reveal that the aerosol comprised particles in two size regimes: (i) approximately spherical ultrafine particles from the gas phase with mean diameter in the 5-10 nm size range and (ii) crystalline, spherical CsI solid droplets with mean diameter of approximately 80 nm formed by splashing of the molten layer on the target surface. (C) 2000 Elsevier Science Ltd. All rights reserved.