  As a minimal model to study charge transfer effects in a transition metal
(TM) and Oxygen (OX) chain, we consider a one-dimensional chain with spinless
fermion with an alternating motif of site-pairs with nearest neighbor (NN)
repulsion $U$ and uncorrelated site-pairs, separated by a charge transfer gap
$\Delta$. We first show that while two holes added in a filled band of NN
interacting fermion in one dimension can stabilize to a two-hole bound pair,
the bound pair delocalizes with a $U$-dependent bandwidth. In contrast, we
establish that the bandwidth of two holes added on a TM site-pair in a filled
band is dramatically suppressed, realizing a `local' two-hole resonance (L2HR)
at the same TM site-pair mimicking the AES phenomenology. Employing a
memory-efficient exact numerical scheme and standard Lanczos-based
diagonalization, we then study two-hole spectra for holes added at TM
site-pairs in partially filled bands. We analyze the multiple features that
arise in the two-hole spectra at partial filling of the ground state. We
uncover that in the strong $U$ limit, there is a filling-dependent
$\Delta_{crit}$ above which the L2HR remains stable for any band-filling
greater than 75\%. In this regime, the energy location of the L2HR provides a
direct estimate of the correlation strength at TM site-pairs for partial
filling and is reminiscent of the Cini-Sawatzky theory for the filled band
case. At 75\% band-filling, an abrupt redistribution of two-hole spectral
weight destroys the L2HR regardless of $U$ or $\Delta$ values. We discuss the
relevance of these nonperturbative results, obtained with full lattice
symmetry, for understanding AES of partially filled bands in terms of the
local-two-hole spectrum.
