Photoionization of clusters in intense few-cycle near infrared femtosecond pulses.

ABSTRACT

In this article we present a perspective on the current state of the art in the photoionization of atomic clusters in few-cycle near-infrared laser pulses. Recently, several studies have reported intriguing phenomena associated with the photoionization of clusters by pulses as short as ~10 fs which approach the natural timescales of collective electronic motion in such nanoscale aggregates. In contrast to the dynamics occurring on few- and sub-picosecond timescales where ionic motion sets in and plays a key role marked by resonant plasmon oscillations, the few-cycle limit precludes cluster expansion due to the nuclear motion of ionic constituents. Thus, pulses lasting just a few optical cycles explore a new "impulsive" regime for the first time in cluster nanoplasmas wherein ions essentially remain "frozen". Along with the perspective on this new regime, we present first measurements of photoelectron distributions and temperatures.