Speaker: Sandra Beauvarlet, University of Bordeaux
Program Description:
In this work, we investigate molecular chirality at femtosecond and attosecond timescales probed by photoelectron dichroism playing with two key parameters : the electric field polarization and its intensity which defines the ionization regime. In resonant multiphoton ionization regime, the photon energy is scanned to reveal the influence of different intermediate states in the chiral response. The ellipticity control allows the selection of a subset of chiral molecules and highlights electronic dynamics and couplings that are not visible in circular polarization. The ellipticity control can then be used in a strong field ionization regime where electron dynamics are driven by the laser field dynamic. In this regime, tuning the ellipticity allows to find a compromise between electron backscattering and chirality of the electric field revealing strong chiral response from these high energy backscattered photoelectrons.
In the following part of the work, the polarization becomes more engineered and structured by combining two-color fields linearly and orthogonaly polarized. This field describing an “8” or a “C” shape has a zero cycle-averaged chirality but variable instantaneous chirality on a time scale smaller than the optical cycle (< 1.7 fs). In strong field regime, we show that photoelectron dichroism is sensitive to sub-fs dynamics of the electric field. This new polarization and sub-cycle interferometry scheme is then combined with attoclock measurements and calculations to study the contributions to the chiral response of electron tunneling and scattering processes occurring in the strong field tunnel ionization. These new chiral observables demonstrate that a chiral sensitive response is imprinted when the electron tunnels through the potential barrier.
Keywords : chiral molecule, ultrafast dynamics, photoelectron, dichroism, ionization regime, polarization scheme
