Multichannel molecular high-order harmonic generation (MHOHG) from a single electron asymmetric molecular ion ${\mathrm{HeH}}^{2+}$ is investigated numerically. It is found that considerable resonant excitation occurs by laser induced electron transfer (LIET) to neighboring ions and multiple frequency (fractional-order) harmonics are observed from the excited states shifted by some energy $\Delta$ from the main $N\omega$ energy harmonics. A time series analysis is used to confirm this MHOHG channel which is created by initial ionization from the excited state prepared by LIET and recombination to the neighboring ion at specific field phases, resulting in interference between recombination pathways from ground and excited states.

• Received 1 March 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.093903