Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Experimental evidence of twin fast metastable H(2S) atoms from
  dissociation of cold H_2 induced by electrons   We report the direct detection of two metastable H(2S) atoms coming from the
dissociation of a single cold H_2 molecule, in coincidence measurements. The
molecular dissociation was induced by electron impact in order to avoid
limitations by the selection rules governing radiative transitions. Two
detectors, placed close from the collision center, measure the neutral
metastable H(2S) through a localized quenching process, which mixes the H(2S)
state with the H(2P), leading to a Lyman-\alpha detection. Our data show the
accomplishment of a coincidence measurement which proves for the first time the
existence of the H(2S)-H(2S) dissociation channel.

35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess