Molecular high-order harmonic generation in a nonlinear two-electron molecule: the equilateral H+3

Abstract

Molecular high-order harmonic generation (MHOHG) is studied from appropriate time-dependent Schrödinger equation (TDSE) solutions of a 2D equilateral two-electron H+3 molecular ion in interaction with an intense (5 × 1014 W cm−2) few-cycle 800 nm linearly polarized laser pulse. The nonperturbative time-dependent Born–Oppenheimer (static nuclei) two-electron wavefunction is used to calculate the MHOHG spectrum as a function of the laser–molecule orientation and internuclear distance R. Three-centre interferences in the MHOHG spectrum are shown to be sensitive functions of the laser–molecule orientation and R. A comparison is made of the MHOHG spectrum at the ground state equilibrium distance, Re, at an intermediate R where a three-photon transition (1A′1 → 1E′) occurs, and finally at internuclear distance Rc where enhanced ionization can occur due to the nonlinear electron–laser interaction. Analytic expressions for MHOHG spectra interferences are derived based on a recollision model and are compared to the exact 2D TDSE simulations.