  Massive young stellar clusters are strong sources of radiation and mechanical
energy. Their powerful winds and radiation pressure sweep-up interstellar gas
into thin expanding shells which trap the ionizing radiation produced by the
central clusters affecting the dynamics and the distribution of their ionized
gas. Here we continue our comparison of the star cluster winds and radiation
pressure effects on the dynamics of shells around young massive clusters. We
calculate the impact that radiation pressure has on the distribution of matter
and thermal pressure within such shells as well as on the density weighted
ionization parameter $U_w$ and put our results on the diagnostic diagram which
allows one to discriminate between the wind-dominated and radiation-dominated
regimes. We found that model predicted values of the ionization parameter agree
well with typical values found in local starburst galaxies. Radiation pressure
may affect the inner structure and the dynamics of wind-driven shells only at
the earliest stages of evolution or if a major fraction of the star cluster
mechanical luminosity is dissipated or radiated away within the star cluster
volume and thus the star cluster mechanical energy output is significantly
smaller than star cluster synthetic models predict. However, even in these
cases radiation dominates over the wind dynamical pressure only if the exciting
cluster is embedded into a high density ambient medium.
