Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear optical response of a gold surface in the visible range: A
  study by two-color sum-frequency generation spectroscopy. II. Model for metal
  nonlinear susceptibility   We present a modeling of the nonlinear optical response of a metal surface in
order to account for recent experimental results from two-color Sum-Frequency
Generation experiments on gold. The model allows calculating the surface and
bulk contributions, and explicitly separates free and bound electron terms.
Contrary to the other contributions, the perpendicular surface component is
strongly model-dependent through the surface electron density profiles. We
consider three electron density schemes at the surface, with free and bound
electrons overlapping or spilling out of the bulk, for its calculation. The
calculated SFG signals from the metal rely only on bulk quantities and do not
need an explicit definition of the density profiles. In the particular case of
gold, when the free electrons overlap with the bound ones or spill out of the
bulk, the free electron response completely dominates through the perpendicular
surface terms. When the bound electrons spill out, the situation is more
balanced, still in favor of the free electrons, with lower amplitudes and
different dispersion lineshapes. As for silver, the free electron contributions
dominate, and the calculated slow amplitude growth from blue to red follows the
experimental trends.

23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph