TIME-DOMAIN SPECTROSCOPY OF MOLECULAR VAPORS WITH SUBPICOSECOND PULSES OF THZ RADIATION

A newly developed optoelectronic beam system generating subpicosecond pulses of THz radiation was used for time-domain studies of N2O vapor. After the excitation the molecules were observed to radiate coherent transients on the free-induction decay originating from the periodic rephasing of coherently excited rotational absorption lines. Numerical simulations of the terahertz pulse propagation through the sample, based on the linear dispersion theory, exactly reproduce the measured pulse structures. Additional calculations of terahertz pulses interacting with OCS and HCN vapor are presented.