Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Watching coherent molecular structural dynamics during photoreaction:
  beyond kinetic description   A deep understanding of molecular photo-transformations is challenging
because of the complex interaction between the configurations of electrons and
nuclei. An initial optical excitation dissipates energy into electronic and
structural degrees of freedom, often in less than one trillionth (10^-12) of a
second. Molecular dynamics induced by photoexcitation have been very
successfully studied with femtosecond optical spectroscopies, but electronic
and nuclear dynamics are often very difficult to disentangle. X-ray based
spectroscopies can reduce the ambiguity between theoretical models and
experimental data, but it is only with the recent development of bright
ultrafast X-ray sources, that key information during transient molecular
processes can be obtained on their intrinsic timescale. In this letter, Free
Electron Laser (FEL) radiation is used to measure ultrafast changes in the
X-ray Absorption Near Edge Structure (XANES) during the prototypical
photoreaction of a spin crossover compound. We reveal its transformation from
the ligand-located electronic photoexcitation to the structural trapping of the
high spin state. The results require a description beyond a kinetic model and
provide a direct observation of a dynamic breathing of the main structural
change. The coherent structural oscillations (period of ~265 fs) in the
photoproduct potential lose synchrony within ~330 fs, whereas incoherent
motions reveal the energy redistribution and vibrational cooling within ~1.6
ps. We foresee that ultrafast X-ray spectroscopies will provide invaluable
insight to understand the complex physics of fundamental light induced
phenomena, which are of prime interest in a multitude of chemical, physical and
biological processes.

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The categories of this paper are: solv-int
19
The categories of this paper are: eess
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The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
16
The categories of this paper are: stat