A4 Article in conference proceedings
ESR investigations of spin-pair radicals in nitrogen-helium solids (2006)

Vehmanen, E., Khmelenko, V., Bernard, E., Kunttu, H., & Lee, D. (2006). ESR investigations of spin-pair radicals in nitrogen-helium solids. AIP Conference Proceedings, . https://doi.org/10.1063/1.2354743

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Publication details

All authors or editors: Vehmanen, Esa; Khmelenko, Vladimir; Bernard, Ethan; Kunttu, Henrik; Lee, David

Journal or series: AIP Conference Proceedings

ISSN: 0094-243X

eISSN: 1935-0465

Publication year: 2006

Number in series: 850

Pages range: 374

Publisher: American Institute of Physics

Publication country: United States

Publication language: English

DOI: https://doi.org/10.1063/1.2354743

Publication open access: Not open

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Abstract

We have investigated nitrogen‐helium solids by X‐band CW‐ESR. Our samples, containing molecules and atoms of either the 14N or the 15N isotope, were produced from N2:He gas mixtures with different nitrogen impurity concentrations ranging from 0.25% to 1%. Samples were formed in a helium cryostat at 1.5 K by applying a radio‐frequency discharge to a gas mixture jet that was then introduced into superfluid 4He. We achieved average concentrations of stabilized nitrogen atoms as high as 2⋅1019 atoms/cm3. We observed a strong ESR signal of stabilized nitrogen atoms at ∼3235 Oe. For the first time we also detected weak ESR signals corresponding to the ΔMS = 2 transitions of 14N⋯14N or 15N⋯15N spin‐pair radicals in nitrogen‐helium solids at ∼1617 Oe. The intensities of these signals were ∼1000 or more times smaller than those of the main atomic signals. We investigated the thermal stability of the nitrogen‐helium solids and observed the spin‐pair radical signals in dry samples at T = 3.1 K. After explosive disintegration of the samples at ∼3.3 K, the spin‐pair radical signal disappeared.

Keywords: helium; emission (physics); particulate emissions

Free keywords: Radiofrequency discharges; Thermodynamic states and processes; Superfluids; Explosives; Chemical elements

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