  Double core-hole (DCH) spectroscopy is investigated systematically for neon
atomic system in the interaction with ultraintense x-ray pulses with photon
energy from 937 eV to 2000 eV. A time-dependent rate equation, implemented in
the detailed level accounting approximation, is utilized to study the dynamical
evolution of the level population and emission properties of the highly
transient plasmas. For x-ray pulses with photon energy in the range of 937-1030
eV, where $1s\rightarrow 2p$ resonance absorption from single core-hole (SCH)
states of neon charge states exist, inner-shell resonant absorption (IRA)
effects play important roles in the time evolution of population and DCH
spectroscopy. Such IRA physical effects are illustrated in detail by
investigating the interaction of x-ray pulses at a photon energy of 944 eV,
which corresponds to the $1s\rightarrow 2p$ resonant absorption from the SCH
states ($1s2s^22p^4$, $1s2s2p^5$ and $1s2p^6$) of Ne$^{3+}$. After averaging
over the space and time distribution of the x-ray pulses, DCH spectroscopy at
photon energies of 937, 944, 955, 968, 980, and 990 eV (corresponding to the
$1s\rightarrow 2p$ resonance energies of Ne$^{2+}$-Ne$^{7+}$, respectively) are
studied in detail. The complex mechanisms of producing the DCH states are
discussed, taking the DCH spectroscopy at 937 and 980 eV as examples. For
photon energy larger than 1362 eV, there are no resonance absorption in the
interaction, resulting in a similar physical picture of DCH spectroscopy. The
dominant DCH states are due to higher ionization stages of Ne$^{7+}$-Ne$^{9+}$,
while the DCH spectroscopy from lower charge states Ne$^{2+}$-Ne$^{6+}$ are
much weaker. With the increase of x-ray photon energy, the contributions from
the lower charge states become larger.
