Laser-induced Coulomb explosion in C and Si nanoclusters: The determining role of pulse duration

► We investigate the interaction of ultrashort laser pulses with small (less than ∼4 nm) carbon and silicon nanoclusters. ► We find that the outer-ionization mechanism goes through a peak for very short (fs) pulses. ► The peak position depends exclusively on pulse duration. ► Other parameters only affect the peak intensity. ► Our results show that Coulomb explosion is almost entirely determined by the pulse duration.