Attosecond Transient Absorption Study of Coherent Hole Oscillation in Ar+

TL;DR

This study demonstrates the observation and control of electron hole oscillations in ionized argon using attosecond transient absorption spectroscopy with MIR and XUV pulses, revealing detailed quantum dynamics and enabling transient state manipulation.

Contribution

It introduces a novel experimental approach combining attosecond spectroscopy with transient control of electron dynamics in argon ions.

Findings

Observed 23 fs hole oscillation beat in Ar+

Simulated transient absorption signals with TDSE and analytic models

Achieved control of absorption via Stark shifts with additional MIR pulse

Abstract

We report on the observation, characterization, and control of the electron dynamics in ionized argon atoms. We utilized an intense mid-infrared (MIR) pulse to create a coherent superposition of the spin-orbit split ground state of the ion. A weak extreme ultraviolet (XUV) pulse then probes the hole oscillation through time-resolved transient absorption spectroscopy. We investigated several 3p to nd transitions accessible with our XUV high harmonics which show a 23fs beat corresponding to the energy separation between the initially populated states. The experimental attosecond transient absorption signals for different pathways were simulated using detailed TDSE simulations and perturbative analytic calculations. The analysis of phase relations between the oscillations reveals important information about transition dipole moments in the system. In addition, we employed another strong MIR pulse to achieve transient control over the absorption by inducing Stark shifts of the states without affecting the electronic coherences.