Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Direct observation of ultrafast long-range charge separation at
  polymer:fullerene heterojunctions
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math