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Short attosecond (as) or few femtoseconds (fs) pulses have a broad energy bandwidth
which allows exciting a superposition of several electronic states in neutral molecules
and molecular cations. The nature of the states excited (valence, Rydberg) can be
controlled by tuning the pulse parameters. This opens the way to novel avenues for
control by engineering of electronic coherences between selected electronic states to
steer charge migration through the selective localization the electronic density on its
purely electronic time scale. 1 As the nuclei begin to move, the electronic and nuclear
motions are entangled and the engineered electronic coherences can be usefully
exploited for steering the vibronic density through the network of non adiabatic
interactions to specific products.
In order to design control schemes built on a selective photoexcitation of electronic
coherences, we analyze the time evolution of the entanglement between nuclear and
electronic degrees of freedom using singular valued decomposition (SVD) of the wave
function. 2 We also derive the expression of the force exerted by the vibronic wave
packet on the nuclei during and after the pulse. 3
I will discuss several examples of the role of initial entanglement induced by the
interaction with an attopulse in the selective fragmentation of diatomic molecules, 3 the
bond formation in a 4C ring closure induced by tuning the parameters of a few cycle
deep UV pulse 4 and the time evolution of the entanglement in the ultrafast structural
rearrangement of the methane cation ionized to a superposition of its three lowest
electronic states. 5
References
1. F. Remacle and R. D. Levine, Proc. Natl. Acad. Sci. USA 103 (18), 6793-6798 (2006); F. Remacle, et
al., Phys. Rev. Lett. 99 (18), 183902 (2007); B. Mignolet, et al., J. Phys. B: At. Mol. Opt. Phys. 47 (12),
124011 (2014).
2. M. Blavier, et al., Phys. Chem. Chem. Phys. 24 (29), 17516-17525 (2022); M. Blavier, et al., Chem.
Phys. Lett. 804, 139885 (2022).
3. M. Cardosa-Gutierrez, R. D. Levine, F. Remacle, 2023, submitted.
4. A. Valentini, et al., Phys. Chem. Chem. Phys. 22 (39), 22302-22313 (2020).
5. C.E.M. Gonçalves, R.D. Levine, F. Remacle, Phys. Chem. Chem. Phys. 23 (2021) 12051-12059, M. |