  We report an experimental and theoretical study of the evolution of
vibrational coherence in a thermal ensemble of nitrogen molecules. Rotational
dephasing and rephasing of the vibrational coherence is detected by coherent
anti-Stokes Raman scattering. The existence of ro-vibrational coupling and the
discrete energy spectrum of the rotational bath lead to a whole new class of
full and fractional ro-vibrational revivals. Following the rich ro-vibrational
dynamics on a nanosecond time scale with sub-picosecond time resolution enables
us to determine the second-order ro-vibrational constant $gamma_e$ and assess
new possibilities of controlling decoherence.
