Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical studies of high-harmonic generation: Effects of symmetry,
  degeneracy and orientation   Using a quantum mechanical three-step model we present numerical calculations
on the high-harmonic generation from four polyatomic molecules. Ethylene
(C$_2$H$_4$) serves as an example where orbital symmetry directly affects the
harmonic yield. We treat the case of methane (CH$_4$) to address the
high-harmonic generation resulting from a molecule with degenerate orbitals. To
this end we illustrate how the single orbital contributions show up in the
total high-harmonic signal. This example illustrates the importance of adding
coherently amplitude contributions from the individual degenerate orbitals.
Finally, we study the high-harmonic generation from propane (C$_3$H$_8$) and
butane (C$_4$H$_{10}$). These two molecules, being extended and far from
spherical in structure, produce harmonics with non-trivial orientational
dependencies. In particular, propane can be oriented so that very
high-frequency harmonics are favorized, and thus the molecule contains
prospects for the generation of UV attosecond pulses.

26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin