Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cross-section and selection rules in surface enhanced hyper Raman
  scattering   The expression for the SEHR cross-section of symmetrical molecules within the
framework of the dipole-quadrupole theory is obtained. It is formed by
contributions, which depend on various dipole and quadrupole moments.
Estimation of the enhancement coefficients for the quadrupole enhancement
mechanism in some limited case can achieve the value . It is demonstrated that
the contributions follow some selection rules. Qualitative classification of
the contributions after the enhancement degree is given.

27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th