Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Efficient X-ray generation from gold colloidal solutions   Hard X-ray generation for Au nanoparticle dispersion was systematically
investigated for different particle diameters ranging from 10 to 100 nm with a
narrow size distribution of +/- 2%. Scaling law of X-ray generation is close to
a 6-photon process before the onset of saturation for excitation by 45 fs laser
pulses with central wavelength of 800 nm. This is consistent with bulk plasmon
excitation at wavelength ~ 138 nm. The longitudinal E-field component due to
nanoparticle focusing is responsible for the excitation of the longitudinal
bulk plasmon. The proposed analysis also explains X-ray emission from water
breakdown via an electron solvation mechanism at ~6.2 eV. The most efficient
emission of X-rays was observed for 40 +/- 10 nm diameter nanoparticles which
also had the strongest UV extinction. X-ray emission was the most efficient
when induced by pre-chirped 370 +/- 20 fs laser pulses and exhibited the
highest intensity at a negative chirp.

3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin