Investigation of nonadiabatic electron dynamics effects on high-harmonic generation spectrum of 𝐇𝟐+

We numerically solved the full-dimensional electronic time-dependent Schrödinger equation for H2+ with Born-Oppenheimer approximation under different sin2-shaped and trapezoidal laser pulses at some different wavelengths, with 𝐼=1×1013, 3×1013 and 6×1013 Wcm-2 intensity at 4.73 a.u. and 7.0 a.u. internuclear distances. Some structures such as minima and oscillatory patterns appearing in the high-order harmonic generation (HHG) spectra are investigated by considering the electron localization, electron nonadiabatic dynamics, and the Rabi frequency of the population of the ground and excited electronic states to better understand the origins of these structures in the HHG spectrum. We have explored that the oscillatory pattern in the HHG spectra originates from an oscillatory pattern in the 𝑆𝑔(𝜔) and 𝑆𝑢(𝜔) (refers to recombination to the 1𝜎𝑔 and 2𝑝𝜎𝑢 respectively) spectra and these oscillatory patterns in turn are due to the nonadiabatic electronic behavior appearing as a slow oscillation pattern in the ground and first excited electronic states populations. Also, we show that the minima of the HHG spectrum are related to 𝑆𝑔(𝜔) , 𝑆𝑢(𝜔), 𝑆𝑔𝑢(𝜔), and orbital interference.