  This paper presents a comprehensive spectroscopic analysis of the nova RS
Ophiuchi during its quiescent stage, spanning a duration of approximately 13
years. The spectra exhibit prominent low-ionization emission features,
including hydrogen, helium, iron, and TiO absorption features originating from
the cool secondary component. The CLOUDY photoionization code is employed to
model these spectra, allowing us to estimate various physical parameters such
as temperature, luminosity, and hydrogen density, along with elemental
abundances and accretion rate. The central ionizing sources exhibit
temperatures in the range of $1.05 - 1.8~\times 10^4$ K and luminosities
between $0.1 - 7.9~\times 10^{30}$ \ergs. Notably, \ion{He}{} displays an
overabundance from 2008 to 2016, returning to solar values by 2020, while
\ion{Fe}{} appears subsolar from 2008 to 2014 but becomes overabundant from
2006 onward. The mean accretion rate, as calculated from the model, is
approximately $1.254 \times 10^{-8} M_{\odot}$ yr$^{-1}$. About 47\% of the
critical mass was accreted after April, 2020 ($\sim$15 months before the 2021
outburst), and approximately 88\% of the critical mass was accreted after July
20, 2018. This non-uniform accretion rate suggests a more rapid approach
towards reaching the critical mass in the final years, possibly attributed to
the heightened gravitational pull resulting from previously accreted matter,
influencing the accretion dynamics as the system approaches the critical mass
limit.
