Ultrafast 2D spectroscopy uses correlated multiple light− matter interactions for retrieving
dynamic features that may otherwise be hidden under the linear spectrum; its extension to
the terahertz regime of the electromagnetic spectrum, where a rich variety of material
degrees of freedom reside, remains an experimental challenge. We report a demonstration
of ultrafast 2D terahertz spectroscopy of gas-phase molecular rotors at room temperature.
Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear …

… Here we present experimental results of THz rotational photon-echo and nonlinear
rotational responses in acetonitrile (CH3CN) resulting from three and five field-dipole
interactions. The time-resolved nonlinear signals are correlated to the transient orientation
of molecular permanent dipoles resonantly driven by THz fields. 2D … We have
experimentally observed THz-field-induced photon echo and 2D rotational spectra in
CH3CN at room temperature. The fully resolved …