Monte Carlo wave-packet approach to trace nuclear dynamics in molecular excited states by XUV-pump–IR-probe spectroscopy

Abstract

Recent research interests have been raised in uncovering and controlling ultrafast dynamics in excited neutral molecules. In this work we generalize the Monte Carlo wave packet (MCWP) approach to XUV-pump-IR-probe schemes to simulate the process of dissociative double ionization of H 2 where singly excited states in H 2 are involved. The XUV pulse is chosen to resonantly excite the initial ground state of H 2 to the lowest excited electronic state of the MCWP approach, a sampling method is proposed to determine in time the dominant ionization events from H 2 to H 2 + . By conducting a trajectory analysis, which is a unique possibility within the MCWP approach, the origins of the characteristic features in the nuclear kinetic energy release spectra are identified for delays ranging from 0 to 140 fs and the nuclear dynamics in the singly excited states in H 2 is mapped out.

Revealing and controlling nuclear dynamics following inner-shell photoionization of N2

“…Apart from the Auger electron energy spectra and the yields of bound N ++ 2 fragments at different Auger energy, we are more interested in recovering the nuclear dynamics involved by obtaining the nuclear KER spectra for different IR pulses with the Monte Carlo wave packet (MCWP) approach. This method has been proven to be especially useful in reproducing the nuclear KER spectra following double ionization of H 2 [31][32][33][34] and O 2 [35]. We will show later that our work can offer clear evidences for the laser-induced couplings between states in N ++ 2 , and thus provides a deeper insight of the dynamics involved in the process of interest.…”

Dynamics of interatomic Coulombic decay in neon dimers by XUV-pump–XUV-probe spectroscopy

“…1). Detailed discussions of its implementation, equivalence with the master equation on the Lindblad form, and validation in pump-probe settings are provided in earlier works [26,31,33]. This method treats ionization as a decay process by adopting a non-Hermitian Hamiltonian.…”

“…For example, we showed in Refs. [29,31] that a trajectory analysis, which is a unique possibility in the MCWP method, is capable of identifying the dominant trajectories contributing the most to a given structure in the nuclear KER spectra and in this way reveal the nuclear dynamics involved.…”

“…Thus, in this case, the final nuclear KER spectrum is obtained by a weighted sum of the KER spectra from the deterministic trajectories as in Ref. [31]. All trajectories after deterministic sampling are successful trajectories ending in the destination channel.…”

“…It was shown in previous works that the Monte Carlo wave-packet (MCWP) approach is especially useful in reproducing the experimental nuclear KER spectra following dissociative double ionization of H 2 [26], D 2 [27], and O 2 [28]. In addition, this method was applied to predict nuclear KER spectra in the dissociative ionization of small molecules in the long wavelength regime [29], a regime that gains increasing experimental interest [30], and more recently the method was extended to describe breakup in XUV-IR pump-probe spectroscopy [31]. In this work, we extend the MCWP approach to accomplish the task of predicting nuclear KER spectra following triple ionization of Ne 2 to resolve the ICD dynamics in Ne 2 .…”