Aleksei S. Kornev

The influence of a permanent dipole moment on the tunnelling ionization of a CO molecule

We show that the linear Stark effect due to a molecule permanent dipole moment does not influence the rate of molecule ionization by laser radiation in the multiphoton limit. However, it may influence the ionization rate in the tunnelling limit. A CO molecule is considered as an example. Its valence orbitals have σ symmetry. In this case, the tunnel effect rate is maximal if the permanent dipole moment (the molecule axis) is oriented along the direction of the laser-wave electric field, and the role of the linear Stark effect is the most noticeable. This situation differs from that when the valence orbitals have π symmetry which we have considered previously (Kornev and Zon 2014 Laser Phys. 24 115302). In that case, the tunnel effect rate is maximal if the molecule axis is oriented perpendicularly to the electric field direction and the role of the linear Stark effect is less significant. We consider the tunnel effect in both dc and ac fields, accounting for perturbation of vibrational motion by an external field. We show that the influence of the permanent dipole moment does not vanish even after averaging the tunnelling rate over the molecule orientations.

Correction to the tunneling theory in atoms

The theory of the tunneling ionization of atoms with several outer-shell electrons is specified. Numerical calculations for the noble-gas atoms are performed.

On the maximum energy of electrons in the presence of a relativistic laser field

As was demonstrated by Milosevic et al. in Phys. Rev. Lett. 92, 013002 (2004), the magnetic component of a light field can be compensated for using counterpropagating matched laser beams. This makes it possible to analyze the rescattering of photoelectrons in the presence of superstrong laser fields. A formula for the maximum energy of a photoelectron is derived for the given configuration of the laser field.

Changes of Normal Coordinates and Geometrical Parameters of a Molecule in a Laser Field

General formulas are derived that describe the changes in equilibrium distances, valence angles, and vibrational frequencies of a polyatomic molecule in a strong laser field. It is shown that the coordinates of normal vibrations do not change in the second order in the field strength. For a nonlinear triatomic molecule of the type of A2B, the changes of geometrical characteristics and vibrational frequencies are obtained in an explicit form.