Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing ultrafast \pi\pi*/n\pi* internal conversion in organic
  chromophores via K-edge resonant absorption   Organic chromophores with heteroatoms possess an important excited state
relaxation channel from an optically allowed {\pi}{\pi}* to a dark
n{\pi}*state. We exploit the element and site specificity of soft x-ray
absorption spectroscopy to selectively follow the electronic change during the
{\pi}{\pi}*/n{\pi}* internal conversion. As a hole forms in the n orbital
during {\pi}{\pi}*/n{\pi}* internal conversion, the near edge x-ray absorption
fine structure (NEXAFS) spectrum at the heteroatom K-edge exhibits an
additional resonance. We demonstrate the concept with the nucleobase thymine, a
prototypical heteroatomic chromophore. With the help of time resolved NEXAFS
spectroscopy at the oxygen K-edge, we unambiguously show that
{\pi}{\pi}*/n{\pi}* internal conversion takes place within (60 \pm 30) fs.
High-level coupled cluster calculations on the isolated molecules used in the
experiment confirm the superb electronic structure sensitivity of this new
method for excited state investigations.

9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex