Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectrum of electronic excitations due to the adsorption of atoms on
  metal surfaces   The time-dependent, mean-field Newns-Anderson model for a spin-polarised
adsorbate approaching a metallic surface is solved in the wide-band limit.
Equations for the time-evolution of the electronic structure of the
adsorbate-metal system are derived and the spectrum of electronic excitations
is found. The behaviour of the model is demonstrated for a set of physically
reasonable parameters.

11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph