Orientation effects in high-order harmonic generation of H$_{2}^{+}$ subject to strong laser fields

We present \textit{ab initio} 3D calculations of the orientation-dependent high-order harmonic generation (HHG) of the hydrogen molecular ion H$_{2}^{+}$ subject to intense linearly polarized laser pulses with the wavelength 800nm [1]. The nuclei are kept at the equilibrium separation of 2 a.u., and the initial electronic state can be either $1\sigma_{g}$ (ground) or $1\sigma_{u}$ (first excited) state. Split-operator technique in the energy represenation and generalized pseudospectral discretization in prolate spheroidal coordinates are used to solve the time-dependent Schr\"odinger equation. HHG power spectra show strong dependence on the orientation angle between the molecular axis and the polarization direction of the laser field. Particularly, orientation-selected resonances with other electronic states are well pronounced. Two-center interference effects in the HHG spectra are also analyzed.\\ 1. D. A. Telnov and S. I. Chu, Phys. Rev. A \textbf{76}, 043412 (2007).