Manipulation of the recombination channels and isolated attosecond pulse generation from HeH²⁺ with multicycle combined field

We present a method to manipulate the recombination channels in harmonic emission from HeH²⁺ via combing a multicycle trapezoidal laser field and a static electric field. By solving the time-dependent Schrödinger equation, we find that the positive peak intensity can steer the electron localization by controlling the electron transfer at the time of laser polarization direction antiparallel to the permanent dipole of HeH²⁺. With appropriate laser parameters, the recombination channels originating from the nucleus He²⁺ are effectively controlled by enhancing electron localization around the nucleus H⁺. Additionally, an isolated 48-as pulse can be obtained by superposing proper harmonics. Time-frequency maps, electronic wave packet probability density and a laser dressed picture of the Coulomb potential are adopted to provide the underlying physical mechanism. (letter)