Reconstruction of the electronic flux during adiabatic attosecond charge migration in HCCI⁺

ABSTRACT

Recently, it was shown that a well-designed laser pulse may prepare an oriented linear molecular ion in a specific superposition state of the electronic ground (g) and first excited (e) states, with different amplitudes and non-zero phases. The reconstruction of the initial state, with time resolution of 100 attoseconds (as), yields the subsequent charge migration that proceeds adiabatically, on the attosecond time scale (AACM). We develop the theory for the time evolutions of the axial density and the flux of the electrons, during AACM. The flux is obtained by simple scaling and time-shifting the results for the ‘reference’ scenario with equal amplitudes and zero phases. Application to the system HCCI⁺ confirms periodic AACM of a rather small number (0.663) of valence electrons, from the acetylenic moiety to the domain of the iodine, and back, with period = 1.85 fs. The underlying axial electronic flux is always unidirectional, with maximum absolute value at the border between the acetylenic moiety and the domain of the iodine, close to the local minimum of the axial density of the valence electrons and to its zero time derivative. The theoretical results imply new challenges for experiment, e.g. one should apply optimal control to steer AACM with maximum electronic flux, and one should investigate its initiation with time resolution below 100 as.

KEYWORDS:

• Attosecond chemistry
• charge migration
• electronic fluxes
• HCCI
• quantum dynamics

Acknowledgments

We would like to dedicate this paper to Professor André Dieter Bandrauk (Sherbrooke) on the occasion of his 75th birthday. One of us (J.M.) expresses his gratitude to André for more than 45 years of friendship in science. We would also like to express sincere thanks to Professor Francoise Remacle and to Dr. Benoit Mignolet (Lille) for explaining some important details of their key paper [1] to us, and to Dr. A. I. Kuleff (Heidelberg) for helpful guidance to part of the quoted literature. Financial support by the Deutsche Forschungsgemeinschaft (project Ma 515/26-1), and the talent program of Shanxi, the Natural Science Foundation of Shanxi, China (2014021004), the Program for Changjiang Scholars and Innovative Research Team (IRT13076), and the National Natural Science Foundation of China (11434007) are also gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Deutsche Forschungsgemeinschaft [project Ma 515/26-1]; the talent program of Shanxi, the Natural Science Foundation of Shanxi, China [Grant Number 2014021004]; the Program for Changjiang Scholars and Innovative Research Team [Grant Number IRT13076]; the National Natural Science Foundation of China [Grant Number 11434007].