  The energy spectrum of a 3-level atomic system in the $\Xi$-configuration is
studied. This configuration presents a triple point independently of the number
of atoms, which remains in the thermo- dynamic limit. This means that in a
vicinity of this point any quantum fluctuation will drastically change the
composition of the ground state of the system. We study the expectation values
of the atomic population of each level, the number of photons, and the
probability distribution of photons at the triple point.

Quantum Physics