|
We will report investigations on the dopant induced ignition of He nanodroplets by intense few-cycle (10 fs) near-infrared (NIR) pulses. This results in the complete ionization of about 10000 He atoms of the droplet which is otherwise transparent to these pulses, droplet triggered by less than 10 dopant atoms residing at the center. These experimental observations aided by a theoretical model demonstrate for the first time, a very efficient absorption and resonant coupling of intense NIR laser fields to cluster nanoplasmas on a 10 fs timescale. We extend the discussion briefly to two-pulse pump-probe studies performed with similar pulses where the effects of doping these large He nanodroplets with a few rare-gas atoms. In this regime, we show that the local charge density gradients play a crucial role in the slow ionic expansion (0.1-1 ps). This results in a prominent dynamical role for the fast expanding shells of He ions which was not recognized in previous experimental studies. Hence, the pump-probe studies reported here call for a revised view of the expansion-induced resonance in these composite nanoplasma systems.
|