Role of dynamic Stark shifts in strong-field excitation and subsequent ionization

Tóth, Attila and Borbély, Sándor and Zhou, Yueming and Csehi, András (2023) Role of dynamic Stark shifts in strong-field excitation and subsequent ionization. PHYSICAL REVIEW A, 107 (5). ISSN 2469-9926

Text Role-of-DSS-accepted.pdf Restricted to Repository staff only Download (1MB) | Request a copy

Abstract

The energy levels of atoms and molecules exposed to intense, short, high-frequency laser pulses undergo time-dependent distortion known as dynamic Stark shift (DSS). These level shifts are in- duced by the coupling with nonresonant (nonessential) states, and follow the temporal intensity profile of the laser pulse. Owing to the different DSSs of the individual atomic levels, transient resonance suppressions and enhancements significantly modify the multiphoton ionization pathway, leaving clear fingerprints (asymmetry, splitting, shifting) in the energy spectrum of emitted photo- electrons. Here we investigate this phenomenon by solving the time-dependent Schr¨odinger equation of the valence electron of Na and Li on increasing levels of complexity: 1) developing minimal mod- els for two-photon transition and 2+1 photon ionization; 2) applying a spectral method without continuum-continuum couplings; 3) propagating the electron wave packet on a large spatial grid accounting for all possible couplings. We show that appropriately detuned transform limited pulses provide a high level of control in strong-field excitation, when the atomic levels are dynamically shifted. Furthermore, we demonstrate the role of DSSs in the multipeak structure of the Autler- Townes doublet, found when several Rabi oscillations are induced during the strong-field resonant ionization.

Actions (login required)

Edit Item