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Updated: Jan 17, 2026

Hyperpolarized Xenon for NMR and MRI Applications
Published on: September 6, 2012
Amplification of Spontaneous Emission from Doubly Excited He Atoms
J Turnšek1,2, Š Krušič1, A Mihelič1,2
1Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia.
Abstract:
We have observed amplification of weak fluorescence from He atoms in the 3a ^{1}P^{o} autoionizing state, which decay by spontaneous emission of 40.74 eV photons in one out of 1600 cases. On average, a 4.1±1.6% conversion of 63.67 eV photons was detected in the forward direction at 20 μJ pump pulse energy and 40 mbar He gas pressure. A comparison with state-of-the-art theoretical simulations shows an unexpected spectral line shift at high gas pressure that is ascribed to transient molecular and electron scattering effects.
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