Overcoming blockade in producing doubly-excited dimers by a single intense pulse and their decay

TL;DR

This paper presents a method using a single intense laser pulse to efficiently produce doubly-excited homoatomic clusters, overcoming excitation blockade, and analyzes their ultrafast decay and ionization processes.

Contribution

It introduces a novel laser pulse technique to overcome excitation blockade in producing doubly-excited dimers, with explicit demonstration on Ne$_2$ and predictions for experimental spectra.

Findings

More than half of dimers can be doubly excited at moderate intensities.

Doubly excited dimers undergo ultrafast decay and ionization.

Predicted electron spectra are reliable for future experiments.

Abstract

Excitation of two identical species in a cluster by the absorption of two photons of the same energy is strongly suppressed since the excitation of one subunit blocks the excitation of the other one due to the binding Coulomb interaction. Here, we propose a very efficient way to overcome this blockade in producing doubly-excited homoatomic clusters by a single intense laser pulse. For Ne$_2$ it is explicitly demonstrated that the optimal carrier frequency of the pulse is given by half of the energy of the target state, which allows one to doubly excite more than half of the dimers at moderate field intensities. These dimers then undergo ultrafast interatomic decay bringing one Ne to its ground state and ionizing the other one. The reported \emph{ab initio} electron spectra present reliable predictions for future experiments by strong laser pulses.