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.
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