Fig. 2: Scheme of TERCE and the time-dependent wave-packet motions.
a Detailed scheme of the TERCE. The electron is firstly ionised to the cation state via tunnelling of the HOMO and HOMO-1 of neutral water, which directly populates the X and A states. With time intervals of a few femtoseconds, the second electron is released via further tunnelling ionisation of the X and A states, and then recollides with the dication and kicks out the third electron, which can be called non-sequential double ionisation (NSDI, indicated as black arrow). Then the trication can dissociate along both the doublet and quartet trication states. The wave-packet evolutions in different states are illustrated as Gaussian distributions. The PESs for 150∘ are offset for the clarity of presentation, and 150∘ is the most probable bond angle for the tunnelling ionisation of A state. b Simulated time-dependent vibrational wave-packets dynamics during TERCE. The X axis stands for the time-delay between single ionisation and double ionisation. T stands for the optical cycle (2.7 fs in our case). The panels P11 to P15 present the vibrational wave-packet (WP) distributions along the X and A states of cation at different time intervals, and are initiated by the tunnelling ionisation of HOMO and HOMO-1. For typical time intervals, the projected wave-packets on dication states are also presented after 2 fs evolutions along the dication (panels P21 to P25). The panels P31 to P35 and P41 to P45 present their corresponding wave-packets before the CE along the doublet and quartet states of the trication, respectively. The electron collision-induced ionisation yields of wave-packets are considered.
