  We propose different spectroscopic methods to explore the nature of the
thermal excitations of a trapped Bose condensed gas: 1) a four photon process
to probe the uniform region in the trap center: 2) a stimulated Raman process
in order to analyze the influence of a momentum transfer in the resulting
scattered atom momentum distribution. We apply these methods to address
specifically the energy spectrum and the scattering amplitude of these
excitations in a transition between two hyperfine levels of the gas atoms. In
particular, we exemplify the potential offered by these proposed techniques by
contrasting the spectrum expected, from the {\it non conserving} Bogoliubov
approximation valid for weak depletion, to the spectrum of the finite
temperature extensions like the {\it conserving} generalized random phase
approximation (GRPA). Both predict the existence of the Bogoliubov collective
excitations but the GRPA approximation distinguishes them from the single atom
excitations with a gapped and parabolic dispersion relation and accounts for
the dynamical screening of any external perturbation applied to the gas. We
propose two feasible experiments, one concerns the observation of the gap
associated to this second branch of excitations and the other deals with this
screening effect.
