Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solid-to-solid phase transition from amorphous carbon to graphite
  nanocrystal induced by intense femtosecond x-ray pulses   We present the results of an experiment where amorphous carbon was irradiated
by femtosecond x-ray free electron laser pulses. The 830 eV laser pulses induce
a phase transition in the material which is characterized ex-situ. The phase
transition energy threshold is determined by measuring the surface of each
irradiated area using an optical Nomarski microscope. The threshold fluence is
found to be 282 +/- 11 mJ/cm^2, corresponding to an absorbed dose at the
surface of 131 +/-5 meV/atom. Atomic force microscopy measurements show volume
expansion of the irradiated sample area, suggesting a solid to solid phase
transition. Deeper insight into the phase transition is gained by using
scanning photoelectron microscopy and micro-Raman spectroscopy. Photoelectron
microscopy shows graphitization, i.e. modification from sp3 to sp2
hybridization, of the irradiated material. The micro-Raman spectra show the
appearance of local order, i.e. formation of graphite nanocrystals. Finally,
the nature of the phase transition is discussed, taking into account previous
theory and experimental results.

10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
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The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex