Quantum State-Resolved Characterization of a Magnetically Focused Beam of ortho-H₂O

Magnetic focusing of a molecular beam formed from a rotationally cooled supersonic jet of H₂O seeded in argon is shown to yield water vapor highly enriched in the ortho-H₂O nuclear spin isomer (NSI). Rotationally resolved resonance-enhanced multiphoton ionization time-of-flight mass spectrometry demonstrates that this methodology enables the preparation of a beam of water molecules enriched to >98% in the ortho-H₂O NSI, that is, having an ortho-to-para ratio in excess of 50:1. The flux and quantum-state purity achieved through the methodology described herein could enable heterogeneous chemistry applications including the preparation of nuclear spin-polarized water adlayers, making nuclear magnetic resonance investigations amenable to surface science studies, as well as laboratory astrophysics investigations of NSI interconversion mechanisms and rates in ice and at its surface.