Multielectron corrections in molecular high-order harmonic generation for different formulations of the strong-field approximation

Abstract

We incorporate multielectron corrections due to exchange and electron–electron correlation in high-order harmonic generation of diatomic molecules in a static and analytic framework. These corrections were incorporated perturbatively around the highest occupied molecular orbital of aligned isoelectronic homonuclear and heteronuclear molecules, exemplified by N₂ and CO, respectively. This is performed for the velocity and length forms of the dipole operator within the framework of the strong field approximation. We find that inclusion of the multielectron corrections has very little effect on the spectrum. This suggests that relaxation, excitation and the dynamic motion of the core are important in order to describe multielectron effects in molecular high-order high harmonic generation. These features are not included in the present model and possibly enhance such effects.

Keywords:

• high-order harmonic generation
• molecules
• strong-field approximation

Acknowledgements

We profited from several discussions with H.J.J. van Dam, P.J. Durham, P. Sherwood and in particular J. Tennyson. This work has been funded by the UK EPSRC (Advanced Research Fellowship, Grant No. EP/D07309X/1 and CASE studentship) and by the Daresbury Laboratory.

Notes

Notes

1. One should note, however, that, in Equation (1), these prefactors are defined as functions of the field-dressed momenta and . These momenta will be different since . Hence, even though the equality holds for field-free momenta.

2. In the standard velocity-gauge formulation for the molecular SFA, the two-centre interference patterns vanish. This happens due to the fact that the gauge transformation will induce a translation in the states which will eliminate the time dependence and lead to a different two-centre interference condition. For details see 15,17.