Pump–Probe Scheme To Study the Autoionization Decay of Optically-Forbidden H₂ Doubly Excited States

Abstract

A pump-probe scheme is proposed to investigate the autoionization dynamics of the optically forbidden Q(1)(1)Σ(g)(+) doubly excited states of the H(2) molecule. The scheme consists of a pump that contains an attosecond pulse train (APT) and an infrared (IR) pulse, which is phase-locked with the APT, and an IR probe identical to the former IR pulse. The dynamical information is obtained by analyzing the electron kinetic energy spectra (EKE) and proton kinetic energy spectra (PKE) as a function of the time delay between the pump and the probe. The essential requirement for an efficient population of the Q(1)(1)Σ(g)(+) states is that they are resonantly coupled to both the dipole-allowed Q(1)(1)Σ(u)(+) doubly excited states and the ground state of H(2) by the combined effect of the APT + IR fields.

Correlated Electron and Nuclear Dynamics in Strong Field Photoionization ofH2+

“…This energy sharing is only efficient within the Franck-Condon region, i.e., in the interval of nuclear-kinetic energies 0.25-0.55 a.u. This is the usual behavior observed in weak-field ionization of diatomic molecules [35][36][37]39], and also, as pointed out very recently, in multiphoton above threshold ionization of H þ 2 [38]. As one increases the intensity without changing the photon energy [ Fig.…”

“…So, ideal experiments are those in which electrons and ions are detected in coincidence [34], since this provides information about how the energy is shared between them. The correlated electron and nuclear dynamics can be visualized by plotting the ionization yield as a function of both the electron and ion kinetic energies [35][36][37][38] (2D plots). State-of-the-art multicoincidence detection techniques are now able to provide such…”

Molecular resolvent-operator method: Electronic and nuclear dynamics in strong-field ionization

“…In such cases, both electron and nuclear dynamics must be considered on an equal footing, and instead of measuring photoelectron and ion spectra separately, it is much more appropriate to measure electrons and ions in coincidence [31], which is now experimentally feasible [32]. The measured ionization yield plotted as a function of both the electron-and ion-kinetic energies [hereafter called for short correlated kinetic energy (CKE) spectrum] thus exhibits the electronic and nuclear dynamics, as well as the connection between them [14,15,19,33]. While most theoretical works on molecules interacting with strong IR fields have reported either KER or EKE spectra, recently, few works (experimental and theoretical) have shown CKE spectra resulting from H 2 + and H 2 photoionization [16,19,34].…”

Ionization behavior of molecular hydrogen in intense laser fields: Influence of molecular vibration and alignment

“…Large differences between the treatment that included the vibrational dynamics and the fixed-nuclei approximation were found [22][23][24]. Later applications of this approach concentrated mainly on low laser intensities and studied, e.g., the decay of autoionizing states [25,26]. Another, more recently introduced approach, again using prolate spheroidal coordinates but Laguerre and Legendre polynomials as basis functions, has been applied to investigate enhanced ionization occurring at large internuclear distances [27].…”