Related Experiment Video
Updated: Mar 12, 2026

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
Published on: October 9, 2012
Excimers in the Lowest Rotational Quantum State in Liquid Helium
Luis Guillermo Mendoza-Luna1, Nagham M K Shiltagh1,2, Mark J Watkins1
1Department of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, United Kingdom.
Abstract:
Evidence for helium excimers (He2*) in the lowest allowed rotational quantum state in liquid helium is presented. He2* was generated by a corona discharge in the gas and normal liquid phases. Fluorescence spectra recorded in the visible region between 3.8 and 5.0 K and 0.2 and 5.6 bar showed the rotationally resolved d3Σu+ → b3Πg transition of He2*. Analysis of the pressure and temperature dependence of lineshifts and line intensities showed features of solvated He2* superimposed on its gas-phase spectrum and, in the liquid phase only, pressure-induced rotational cooling. These findings suggest that He2* can be used to investigate bulk helium in different phases at the nanoscale.
Related Concept Videos
Atomic Nuclei: Nuclear Spin State Population Distribution
The Pauli Exclusion Principle
Atomic Nuclei: Nuclear Spin State Overview
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
UV–Vis Spectroscopy: Molecular Electronic Transitions
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals

