Effects of nanosecond electromagnetic pulses on metallic (Al) and semiconductor (Si, GaAs) surfaces were investigated exptl. in vacuum. For the surface c.d. 104-106 Wcm-2, an impulse desorption of ions was obsd. from adsorbed gaseous layers or deposited org. mols. Desorbed ions were selected and detected by means of a time-of-flight mass analyzer. The phys. mechanisms of desorption are discussed. [on SciFinder (R)]