Two-dimensional terahertz spectroscopy of vibrational modes in a molecular solid.*

Molecular vibration modes are a basic excitation in molecular solids. It’s coupling with other dynamic process influences the relaxation channel of atoms, electrons and spins.

Two-dimension (2D) THz is a useful method to study molecular  vibrations, rotations, dielectric relaxations, electron and spin excitations, and particularly to reveal the coupling between different degrees of freedom. By using high field THz pulses, we have measured the 2D nonlinear transmission spectrum on a single molecular magnet powder, and analyzed the different contributions to the nonlinear signal.  The 2D nonlinear signal indicates a dynamic coupling between the vibrational modes and other degrees of freedom.