ABSTRACT
The emerging field of cold molecules offers applications ranging from novel studies of light-molecule interactions (e.g., coherences within rotational states) over interactions between dipolar molecules [1], to ultrahigh-resolution spectroscopy, and to the study of complex systems [2]. In spectroscopy, a similar qualitative jump is expected as was obtained in atomic spectroscopy after the technique of laser cooling was introduced. Vibrational and rotational levels of suitable molecules have long lifetimes (milliseconds to days), implying potentially huge transition quality factors. Fundamental physics experimentswithmolecules requiring extreme resolution and accuracy include tests of quantum electrodynamics (QED), measurement of and search for a space-time variability of the proton-to-electron mass ratio [3], the search for parity violation effects on vibrational transition frequencies [4,5], and tests of the isotropy of space [6]. Finally, a novel application is the investigation of collisions of molecules with atoms or othermolecules at very low temperatures [7,8]. This temperature regime represents a unique situation for the studyof quantum-mechanical details of collisional processes, preferably with the collision partners in well-defined internal states [9].
