  We present observations from our continuing studies of the earliest stages of
massive star cluster evolution. In this paper, radio observations from the Very
Large Array at 0.7cm, 1.3cm, 2cm, 3.6cm, and 6cm are used to map the radio
spectral energy distributions and model the physical properties of the
ultra-young embedded super star clusters in Henize 2-10. The 0.7cm flux
densities indicate that the young embedded star clusters that are powering the
radio detected ``ultradense HII regions'' (UDHIIs) have masses greater than
\~10^5 Msun. We model the radio spectral energy distributions as both constant
density HII regions and HII regions with power-law electron density gradients.
These models suggest the UDHIIs have radii ranging between ~2-4pc and average
electron densities of ~10^3-10^4 cm^-3 (with peak electron densities reaching
values of ~10^5-10^6 cm^-3). The pressures implied by these densities are
P/k_B~10^7-10^10 cm^-3 K, several orders of magnitude higher than typical
pressures in the Galactic ISM. The inferred HII masses in the UDHIIs are
\~2-8x10^3 Msun; these values are <5% of the embedded stellar masses, and
anonamously low when compared to optically visible young clusters. We suggest
that these low HII mass fractions may be a result of the extreme youth of these
objects.
