Time-dependent quantum wave packet simulation for strong laser-induced molecular dynamics in multiple electronic states of H₂ molecules

We present a fully time-dependent quantum wave packet evolution method for investigating molecular dynamics in intense laser fields. This approach enables the simultaneous treatment of interactions among multiple electronic states while simultaneously tracking their time-dependent electronic, vibrational, and rotational dynamics. As an illustrative example, we consider neutral H₂ molecules and simulate the laser-induced excitation dynamics of electronic and rotational states in strong laser fields, quantitatively distinguishing the respective contributions of electronic dipole transitions (within the classical-field approximation) and non-resonant Raman processes to the overall molecular dynamics. Furthermore, we precisely evaluate the relative contributions of direct tunneling ionization from the ground state and ionization following electronic excitation in the strong-field ionization of H₂. The developed methodology shows strong potential for performing high-precision theoretical simulations of electronic-vibrational-rotational state excitations, ionization, and dissociation dynamics in molecules and their ions under intense laser fields.