Photoabsorption of attosecond XUV light pulses by two strongly laser-coupled autoionizing states

TL;DR

This paper provides a theoretical analysis of how attosecond XUV pulses are absorbed by a laser-dressed atomic system with autoionizing states, explaining recent experimental results and exploring the effects of laser coupling and Rabi flopping.

Contribution

It introduces a theoretical framework for understanding XUV photoabsorption in laser-coupled autoionizing states, connecting spectral features with laser parameters and autoionization dynamics.

Findings

Laser coupling modifies absorption spectra significantly.

Rabi flopping influences autoionization and spectral features.

Theoretical results align with recent experimental observations.

Abstract

We study theoretically the photoabsorption spectra of an attosecond XUV pulse by a laserdressed atomic system. A weak XUV excites an autoionizing state which is strongly coupled to another autoionizing state by a laser. The theory was applied to explain two recent experiments [Loh, Greene, and Leone, Chem. Phys. 350, 7 (2008); Wang, Chini, Chen, Zhang, Cheng, He, Cheng, Wu, Thumm, and Chang, Phys. Rev. Lett. 105 143002 (2010)] where the absorption spectra of the XUV lights were measured against the time delay between the laser and the XUV. In another example, we study an attosecond pulse exciting the 2s2p(1P) resonance of helium which is resonantly coupled to the 2s2(1S) resonance by a moderately intense 540 nm laser. The relation between the photoabsorption spectra and the photoelectron spectra and the modification of the transmitted lights in such an experiment are analyzed. The role of Rabi flopping between the two autoionizing states within their lifetimes is investigated with respect to the laser intensity and detuning.