C. Varin | Searcharxiv

arXiv2012

Unipolar components travelling at the speed of light in vacuo

We describe a physical situation where the time integral of the electric field of an electromagnetic wave packet is not zero. More specifically, the non-oscillating component of the Fourier spectrum, i.e. the component resulting from the Fourier transform of the electric field evaluated at $ω=0$, can be associated with the area under a locally unipolar electromagnetic pulse that travels in free space at the speed of light.

physics.class-ph↗

arXiv2010

Steplike intensity threshold behavior of extreme ionization in laser-driven Xe clusters

The generation of highly charged Xe$^{q+}$ ions up to {$q=24$} is observed in Xe clusters embedded in helium nanodroplets and exposed to intense femtosecond laser pulses ($λ$=800 nm). Laser intensity resolved measurements show that the high-$q$ ion generation starts at an unexpectedly low threshold intensity of about {10$^{14}$ W/cm$^{2}$}. Above threshold, the Xe ion charge spectrum saturates quickly and changes only weakly for higher laser intensities. Good agreement between these observations and a molecular dynamics analysis allows us to identify the mechanisms responsible for the highly charged ion production and the surprising intensity threshold behavior of the ionization process.

physics.atm-clus↗