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arXiv · 2112.10008

Theoretical analysis of the role of complex transition dipole phase in XUV transient-absorption probing of charge migration

Yuki Kobayashi·Daniel M. Neumark·Stephen R. Leone
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Abstract

We theoretically investigate the role of complex dipole phase in the attosecond probing of charge migration. The iodobromoacetylene ion (ICCBr$^+$) is considered as an example, in which one can probe charge migration by accessing both the iodine and bromine ends of the molecule with different spectral windows of an extreme-ultraviolet (XUV) pulse. The analytical expression for transient absorption shows that the site-specific information of charge migration is encoded in the complex phase of cross dipole products for XUV transitions between the I-$4d$ and Br-$3d$ spectral windows. Ab-initio quantum chemistry calculations on ICCBr$^+$ reveal that there is a constant $π$ phase difference between the I-$4d$ and Br-$3d$ transient-absorption spectral windows, irrespective of the fine-structure energy splittings. Transient absorption spectra are simulated with a multistate model including the complex dipole phase, and the results correctly reconstruct the charge-migration dynamics via the quantum beats in the two element spectral windows, exhibiting out-of-phase oscillations.

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Yuki Kobayashi, Daniel M. Neumark, Stephen R. Leone. 2021-12-14. Theoretical analysis of the role of complex transition dipole phase in XUV transient-absorption probing of charge migration. https://doi.org/10.1364/oe.451129

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