Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct measurement of desorption and diffusion energies of O and N atoms
  physisorbed on amorphous surfaces   Physisorbed atoms on the surface of interstellar dust grains play a central
role in solid state astrochemistry. Their surface reactivity is one source of
the observed molecular complexity in space. In experimental astrophysics, the
high reactivity of atoms also constitutes an obstacle to measuring two of the
fundamental properties in surface physics, namely desorption and diffusion
energies, and so far direct measurements are non-existent for O and N atoms. We
investigated the diffusion and desorption processes of O and N atoms on cold
surfaces in order to give boundary conditions to astrochemical models. Here we
propose a new technique for directly measuring the N- and O-atom mass signals.
Including the experimental results in a simple model allows us to almost
directly derive the desorption and diffusion barriers of N atoms on amorphous
solid water ice (ASW) and O atoms on ASW and oxidized graphite. We find a
strong constraint on the values of desorption and thermal diffusion energy
barriers. The measured barriers for O atoms are consistent with recent
independent estimations and prove to be much higher than previously believed
(E$_{des}=1410_{-160}^{+290}$; E$_{dif}=990_{-360}^{+530}$ K on ASW). As for
oxygen atoms, we propose that the combination E$_{des}$-E$_{dif}$=1320-750 K is
a sensible choice among the possible pairs of solutions. Also, we managed to
measure the desorption and diffusion energy of N atoms for the first time
(E$_{des}=720_{-80}^{+160}$; E$_{dif}=525_{-200}^{+260}$ K on ASW) in the
thermal hopping regime and propose that the combination
E$_{des}$-E$_{dif}$=720-400 K can be reasonably adopted in models. The value of
E$_{dif}$ for N atoms is slightly lower than previously suggested, which
implies that the N chemistry on dust grains might be richer.

12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
2
The categories of this paper are: math
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg