Time-resolved investigation of transient charges in laser-produced nanoplasmas

We report on the observation of a transient C⁴⁺ ion charge state in nanoplasmas produced by the interaction of intense near-infrared (NIR) laser pulses with CH₄ clusters. The underlying dynamics are studied by pump-probe spectroscopy, which reveals that the ion charge states are lowered by electron-ion recombination. Furthermore, we present direct evidence that autoionization of multiply-excited ions plays an important role in expanding nanoplasmas, in contrast to models that neglect quantum phenomena. (paper)