Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perspective: Accurate ro-vibrational calculations on small molecules   In what has been described as the fourth age of Quantum Chemistry,
variational nuclear motion programs are now routinely being used to obtain the
vibration-rotation levels and corresponding wavefunctions of small molecules to
the sort of high accuracy demanded by comparison with spectroscopy. In this
perspective I will discuss the current state-of-the-art which, for example,
shows that these calculations are increasingly competitive with measurements
or, indeed, replacing them and thus becoming the primary source of data on key
processes. To achieve this accuracy {\it ab initio} requires consideration
small effects, routinely ignored in standard calculations, such those due to
quantum electrodynamics (QED). Variational calculations are being used to
generate huge list of transitions which provide the input for models of
radiative transport through hot atmospheres and to fill in or even replace
measured transition intensities. Future prospects such as study of molecular
states near dissociation, which can provide a link with low-energy chemical
reactions, are discussed.

31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex