Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evolution from a molecular Rydberg gas to an ultracold plasma in a
  seeded supersonic expansion of NO   We report the spontaneous formation of a plasma from a gas of cold Rydberg
molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1
K in a seeded supersonic molecular beam, to single Rydberg states extending as
deep as 80 cm$^{-1}$ below the lowest ionization threshold. The density of
excited molecules in the illuminated volume is as high as 1 x 10$^{13}$
cm$^{-3}$. This population evolves to produce prompt free electrons and a
durable cold plasma of electrons and intact NO$^{+}$ ions.

36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph