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Abstract Conical intersections between electronic states often dictate the chemistry of photoexcited molecules. Recently developed sources of ultrashort extreme ultraviolet (XUV) pulses tuned to element-specific transitions in molecules allow for the unambiguous detection of electronic state-switching at a conical intersection. Here, the fragmentation of photoexcitediso-propyl iodide andtert-butyl iodide molecules (i-C3H7I andt-C4H9I) through a conical intersection between3Q0/1Q1spin–orbit states is revealed by ultrafast XUV transient absorption measuring iodine 4dcore-to-valence transitions. The electronic state-sensitivity of the technique allows for a complete mapping of molecular dissociation from photoexcitation to photoproducts. In both molecules, the sub-100 fs transfer of a photoexcited wave packet from the3Q0state into the1Q1state at the conical intersection is captured. The results show how differences in the electronic state-switching of the wave packet ini-C3H7I andt-C4H9I directly lead to differences in the photoproduct branching ratio of the two systems.
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Theoretical analysis of the role of complex transition dipole phase in XUV transient-absorption probing of charge migration
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-4dand Br-3dspectral windows. Ab-initio quantum chemistry calculations on ICCBr+reveal that there is a constantπphase difference between the I-4dand Br-3dtransient-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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- PAR ID:
- 10531101
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 30
- Issue:
- 4
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 5673
- Size(s):
- Article No. 5673
- Sponsoring Org:
- National Science Foundation
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