  We examine pairing and molecule formation in strongly-interacting Fermi
gases, and we discuss how radio-frequency (RF) spectroscopy can reveal these
features.
  For the balanced case, the emergence of stable molecules in the BEC regime
results in a two-peak structure in the RF spectrum with clearly visible medium
effects on the low-energy part of the molecular wavefunction.
  For the highly-imbalanced case, we show the existence of a well-defined
quasiparticle (a spin polaron) on both sides of the Feshbach resonance, we
evaluate its lifetime, and we illustrate how its energy may be measured by RF
spectroscopy.
