Terahertz time-domain spectroscopy of water vapor

We describe the application of a new high-brightness, terahertz-beam system to time-domain spectroscopy. By analyzing the propagation of terahertz electromagnetic pulses through water vapor, we have made what we believe are the most accurate measurements to date of the absorption cross sections of the water molecule for the nine strongest lines in the frequency range from 0.2 to 1.45 THz. © 1989 Optical Society of America.