Angular Dependence of Laser-Induced Electron Rescattering in Molecules

Abstract

We report on the retrieval of the angular dependence of laser-induced electron rescattering in CO2 with a novel method from the measured rotational half revival signals of filed-free aligned molecules using a reaction microscope.

Laser-induced valence electron excitation in acetylene

“…In general, in these experiments, the driving laser field is a non-resonant field with respect to the molecular energy level structure. The four most common processes are 1) electron excitation through laserinduced strong-field ionization from low-lying molecular orbitals [5,[8][9][10][11][12][13]; 2) electron excitation through laser-induced electron rescattering after strong-field ionization [14][15][16][17]; 3) laserinduced electron excitation through single-or multi-photon transitions after strong-field ionization (so-called bond softening process) [18][19][20][21]; and 4) laser-induced electron recapture to electron excited states after strong-field ionization [22][23][24][25]. All four electron excitation processes start with strongfield ionization.…”

“…One important feature of molecular strong-field ionization in a strong laser field is that the ionization rate depends on the angle between the molecular axis and the laser polarization direction [5,13,[26][27][28][29]. The angular ionization probability of a molecule is determined by the shape and symmetry of the involved molecular orbitals [30].…”

“…For example, strong-field ionization of electrons from the HOMO of C 2 H 2 , a π-orbital, reaches a maximum when the laser is polarized perpendicular to the molecular axis, while for the ionization from a σ-orbital, the maximum ionization probability appears when the laser polarization direction is parallel to the molecular axis [5]. Therefore, using the angular dependence of strong-field ionization, we could determine the contributions from certain molecular orbitals in experiments [13].…”