Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tracing transient charges in expanding clusters   We study transient charges formed in methane clusters following ionization by
intense near-infrared laser pulses. Cluster ionization by 400 fs ($I=1 \times
10^{14}$ W/cm$^2$) pulses is highly efficient, resulting in the observation of
a dominant C$^{3+}$ ion contribution. The C$^{4+}$ ion yield is very small, but
is strongly enhanced by applying a time-delayed weak near-infrared pulse. We
conclude that most of the valence electrons are removed from their atoms during
the laser-cluster interaction, and that electrons from the nanoplasma recombine
with ions and populate Rydberg states when the cluster expands, leading to a
\textit{decrease} of the average charge state of individual ions. Furthermore,
we find clear bound-state signatures in the electron kinetic energy spectrum,
which we attribute to Auger decay taking place in expanding clusters. Such
nonradiative processes lead to an \textit{increase} of the final average ion
charge state that is measured in experiments. Our results suggest that it is
crucial to include both recombination and nonradiative decay processes for the
understanding of recorded ion charge spectra.

27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
19
The categories of this paper are: eess