Ultrafast ionization of atoms or molecules by intense laser pulses creates extremely non-stationary ionic states. This process triggers attosecond correlated electron-hole dynamics and subsequent ultrafast non-equilibrium evolution of matters. Here we investigate the interwoven dynamic evolutions of neutral nitrogen molecules together with nitrogen ions created through transient tunnel ionization in an intense laser field. Based on the proposed theoretical frame, it is found that nitrogen molecular ions are primarily populated in the electronically excited states, rather than staying in the ground state as predicted by the well-known tunneling theory. The unexpected result is attributed to sub-cycle switch-on of time-dependent polarization by transient ionization and dynamic Stark shift mediated near-resonant multiphoton transitions. These findings corroborate the mechanism of nitrogen molecular ion lasing and are likely to be universal. The present work opens a route to explore the important role of transient ionization injection in strong-field induced non-equilibrium dynamics.

原子或分子通过强激光脉冲超快电离会产生极其不稳定的离子态。此过程触发了与原子相关的阿秒级动力学，并随后引发了物质的超快速非平衡演化。在这里，我们研究在强烈的激光场中，中性氮分子与通过瞬态隧道电离产生的氮离子的交织动态演变。基于提出的理论框架，发现氮分子离子主要以电子激发态填充，而不是像众所周知的隧穿理论所预测的那样停留在基态。出乎意料的结果归因于瞬态电离和动态Stark位移介导的近共振多光子跃迁的时间依赖性极化的子周期开启。这些发现证实了氮分子离子激射的机制，并且可能是普遍的。本工作为探索瞬态电离注入在强场诱导的非平衡动力学中的重要作用开辟了道路。