Dressing Effects in the Attosecond Transient Absorption Spectra of Doubly-Excited States in Helium

29th International Conference on Photonic, Electronic, and Atomic Collisions

Argenti, L.^1 ; Jiménez-Galán, Á.^1 ; Marante, C.^1 ; Ott, C.^2,3 ; Pfeifer, T.^2,3 ; Martín, F.^1,4,5

Departamento de Química, Universidad Autónoma de Madrid, Módulo 13, Cantoblanco, Madrid

28049, Spain^1

Max-Planck Institut für Kernphysik, Saupfercheckweg 1, Heidelberg

69117, Germany^2

Center for Quantum Dynamics, Ruprecht-Karls-Universität Heidelberg, Heidelberg

69120, Germany^3

Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid

28049, Spain^4

IMDEA-Nanociencia, Cantoblanco, Madrid

28049, Spain^5

关键词: Ab initio calculations;    Autoionizing series;    Autoionizing state;    Doubly excited state;    Electronic quantum;    Experimental spectra;    Ponderomotive energy;    Transient absorption spectra;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/635/9/092015/pdf
DOI  :  10.1088/1742-6596/635/9/092015

来源: IOP

【 摘 要 】

Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum (ATAS) of helium dressed by a few-cycle visible pulse [C. Ott et al, Nature 516, 374 (2014)] provide evidence of the inversion of Fano profiles. With the support of accurate ab-initio calculations that reproduce the results of the latter experiment, here we investigate the new physics that arise from ATAS when the laser intensity is increased. In particular, we show that (i) previously unnoticed signatures of the dark 2p2 1S doubly excited state are observed in the experimental spectrum, (ii) inversion of Fano profiles is predicted to be periodic in the laser intensity, and (iii) the ac-Stark shift of the higher terms in the sp+2, nautoionizing series exceeds the ponderomotive energy, which is the result of a genuine two-electron contribution to the polarization of the excited atom.