Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Manipulation of the electronic structure by reversible dehydrogenation
  of tetra(p-hydroxyphenyl)porphyrin molecules   The controlled and reversible interconversion between the free-base and the
doubly dehydrogenated form of a 5,10,15,20-tetra(p-hydroxyphenyl)porphyrin
molecule in an ordered array is demonstrated. This is achieved through voltage
pulses by hydrogen transfer between the center of the porphyrin and the tip of
a scanning tunneling microscope (STM). The local dehydrogenation leads to
significant shifts in the energetic positions of the molecular orbitals.
Density functional theory (DFT) calculations corroborate our conclusions and
allow to gain more insight into the different energy level alignment before and
after dehydrogenation. Due to the different conductance at a given voltage a
clear distinction of both molecular species is possible, which also enables the
application as a single-molecular switch.

13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th