Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-Energy X-Ray Standards from Hydrogenlike Pionic Atoms   We demonstrate the first step of a complete program, which consists in
establishing an x-ray energy standard scale with the use of few-body atoms, in
the few keV range. Light pionic and muonic atoms as well as one and
two-electron ions from electron-cyclotron ion sources are used. The transition
energies are calculable from quantum-electrodynamics, meaning that only a very
limited subset need be measured and compared with theory, while providing a
large number of standard lines. Here we show that circular transitions in
pionic neon atoms, completely stripped from their electrons, reveal spectral
lines which are narrow, symmetric, and well reproducible. We use these lines
for the energy determination of transition energies in complex electronic
systems, like the K1,2 transitions in metallic Ti, which may serve as secondary
standard.

8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat