  Small, illuminated aerosol particles embedded in a gas experience a
photophoretic force. Most approximations assume the mean particle surface
temperature to be effectively the gas temperature. This might not always be the
case. If the particle temperature or the thermal radiation field strongly
differs from the gas temperature (optically thin gases), given approximations
for the free molecule regime overestimate the photophoretic force by an order
of magnitude on average and for individual configurations up to three
magnitudes. We apply the radiative equilibrium condition from the previous
paper (Paper 1) -- where photophoresis in the free molecular flow regime was
treated -- to the slip flow regime. The slip-flow model accounts for thermal
creep, frictional and thermal stress gas slippage and temperature jump at the
gas-particle interface. In the limiting case for vanishing Knudsen numbers --
the continuum limit -- our derived formula has a mean error of only 4 \%
compared to numerical values. Eventually, we propose an equation for
photophoretic forces for all Knudsen numbers following the basic idea from
Rohatschek by interpolating between the free molecular flow and the continuum
limit.
