Dynamical Molecular Electron Momentum Densities, Symmetry or Molecular Dressed States and Molecular Plasmons

Abstract

Light-matter interaction in different frequency regimes has been a continual subject of inquest, and increasingly so, owing to the development of ultra-fast, few-cycle laser technologies. While time- dependent position-space electronic properties of matter have been explored to a decent extent, the same cannot be said for momentum-space properties. Valence electrons, which are the most affected in the presence of a laser, are better represented and described by momentum-space quantities since the valence electrons are transformed onto the low momenta regions. An interesting advantage is the sensitivity of electronic properties in this space to any external perturbation. Further, in the presence of femtosecond and attosecond lasers, phenomena such as ionization, emission and higher-harmonic generation (HHG) ensue, discerning which is important for understanding strong-field chemistry. The work presented here includes a point group-based classification of laser-dressed molecules, using the higher-order terms of the Kramers-Henneberger potential, to come up with a prescription for selection rules in HHG. In addition, molecular plasmons, defined as collective oscillations of the electronic density as a result of interferences between individual electronic transitions, have also been looked at. One-electron properties such as electron density and molecular electrostatic potential have been used to quantify the signature of a molecular plasmon as a least electronic rearrangement excited state.