  We analyze the thermal Casimir-Polder potential experienced by a ground-state
molecule in a planar cavity and investigate the prospects for using such a
set-up for molecular guiding. The resonant atom-field interaction associated
with this non-equilibrium situation manifests itself in oscillating,
standing-wave components of the potential. While the respective potential wells
are normally too shallow to be useful, they may be amplified by a highly
reflecting cavity whose width equals a half-integer multiple of a particular
molecular transition frequency. We find that with an ideal choice of molecule
and the use of ultra-high reflectivity Bragg mirror cavity, it may be possible
to boost the potential by up to two orders of magnitude. We analytically derive
the scaling of the potential depth as a function of reflectivity and analyze
how it varies with temperature and molecular properties. It is also shown how
the potential depth decreases for standing waves with a larger number of nodes.
Finally, we investigate the lifetime of the molecular ground state in a thermal
environment and find that it is not greatly influenced by the cavity and
remains in the order of several seconds.
