Molecular high-order harmonic generation in a nonlinear two-electron molecule: the equilateral H3+

Molecular high-order harmonic generation (MHOHG) is studied from appropriate time-dependent Schrodinger equation (TDSE) solutions of a 2D equilateral two-electron H-3(+) molecular ion in interaction with an intense (5 x 10(14) 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, R-e, at an intermediate R where a three-photon transition ((1)A(1)' -> E-1') occurs, and finally at internuclear distance R-c 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.