  We use an optical centrifuge to excite coherent rotational wave packets in
N$_2$O, CS$_2$ and OCS molecules with rotational quantum numbers reaching up to
J=465, 690 and 1186, respectively. Time-resolved rotational spectroscopy at
such ultra-high levels of rotational excitation can be used as a sensitive tool
to probe the molecular potential energy surface at inter-nuclear distances far
from their equilibrium values. Significant bond stretching in the centrifuged
molecules results in the growing period of the rotational revivals, which are
experimentally detected using coherent Raman scattering. We measure the revival
period as a function of the centrifuge-induced rotational frequency and compare
it with the numerical calculations based on the known Morse-cosine potentials.
