Related Experiment Video
Updated: Apr 30, 2026

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Zeeman-tuned rotational level-crossing spectroscopy in a diatomic free radical
S B Cahn1, J Ammon1, E Kirilov1
1Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520, USA.
Abstract:
Rotational levels of molecular free radicals can be tuned to degeneracy by using laboratory-scale magnetic fields. Because of their intrinsically narrow width, these level crossings of opposite-parity states have been proposed for use in the study of parity-violating interactions and other applications. We experimentally study a typical manifestation of this system using BaF138. Using a Stark-mixing method for detection, we demonstrate level-crossing signals with spectral width as small as 6 kHz. We use our data to verify the predicted line shapes, transition dipole moments, and Stark shifts and to precisely determine molecular magnetic g factors. Our results constitute an initial proof of concept for use of this system to study nuclear spin-dependent parity-violating effects.
More Related Videos
Related Concept Videos
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
Radical Reactivity: Overview
Molecular Spectroscopy: Absorption and Emission
UV–Vis Spectroscopy: Molecular Electronic Transitions
Radical Formation: Overview
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the...
Radicals: Electronic Structure and Geometry
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...

