  An electro-optic dual comb system based on chirped-pulse waveforms is used to
simultaneously acquire temporally magnified rapid passage signals and normal
spectral line shapes from the back-transformation to the time domain.
Multi-heterodyne THz wave generation and detection is performed with the
difference frequency mixing of two free-running lasers. The method is used to
obtain THz spectra of formic acid in the 10 cm-1 to 20 cm-1 (300 GHz to 600
GHz) region over a range of pressures. The method is widely applicable across
other spectral regions for investigations of the transient dynamics and
spectroscopy of molecular systems.
