Role of excited states in the emission times of harmonics from asymmetric molecules

We investigate the emission times of high-order harmonics from the asymmetric molecule HeH2 ⁺ exposed to intense laser fields numerically and analytically. We show that for each laser cycle, the emission times of harmonics follow two characteristic electron trajectories. The first one matches the prediction of the general ground-state-based quantum orbital theory (GSB-QOT), as the second one differs significantly from the GSB-QOT. We show that the excited state plays an important role in this difference. As a result, the emission times of harmonics can be used as a tool to monitor the dynamics of excited states of the asymmetry molecule in strong laser fields.