  We trap cold, ground-state, argon atoms in a deep optical dipole trap
produced by a build-up cavity. The atoms, which are a general source for the
sympathetic cooling of molecules, are loaded in the trap by quenching them from
a cloud of laser-cooled metastable argon atoms. Although the ground state atoms
cannot be directly probed, we detect them by observing the collisional loss of
co-trapped metastable argon atoms using a new type of parametric loss
spectroscopy. Using this technique we also determine the polarizability ratio
between the ground and the metastable 4s[3/2]$_2$ state to be 40$\pm6$ and find
a polarisability of (7.3$\pm$1.1) $\times$10$^{-39}$ Cm$^2/$V for the
metastable state. Finally, Penning and associative losses of metastable atoms,
in the absence of light assisted collisions, are determined to be $(3.3\pm 0.8)
\times 10^{-10}$ cm$^3$s$^{-1}$.
