title: Separating para and ortho water.
abstract: Water exists as two nuclear-spin isomers, para and ortho, determined by the overall spin of its two hydrogen nuclei. For isolated water molecules, the conversion between these isomers is forbidden and they act as different molecular species. Yet, these species are not readily separated, and no pure para sample has been produced. Accordingly, little is known about their specific physical and chemical properties, conversion mechanisms, or interactions. The production of isolated samples of both spin isomers is demonstrated in pure beams of para and ortho water in their respective absolute ground state. These single-quantum-state samples are ideal targets for unraveling spin-conversion mechanisms, for precision spectroscopy and fundamental symmetry-breaking studies, and for spin-enhanced applications, for example laboratory astrophysics and astrochemistry or hypersensitized NMR experiments.
authors.affiliation: Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany) http://desy.cfel.de/cid/cmi/
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Horke
authors.forename: Yuan-Pin
authors.initials: YP
authors.lastname: Chang
authors.forename: Karol
authors.initials: K
authors.lastname: Długołęcki
authors.forename: Jochen
authors.initials: J
authors.lastname: Küpper
keywords: cold molecules; isomers; laser spectroscopy; nuclear-spin separation; quantum-state selection