Polarization Spectroscopy of Pendular Molecules in the Gas Phase

Orientation of polar or paramagnetic molecules in a uniform electric or magnetic field elegantly reduces congestion in laser spectra of electronic transitions. For room-temperature samples the intensity distribution of polarization spectra concentrates at the band head of rotational branches as it normally would at a temperature of a few Kelvin. Moreover, some rotational branches are eliminated entirely, so resolution increases without loss of information. Experimental procedure and a quantitative simulation of polarization spectra of pendular molecules are demonstrated for the ICl molecule (diagram), and extension to larger molecules is discussed.