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Two-Photon Absorption by Hydrogen Molecules: Origin of the 2175 Angstrom Astronomical Band?

Peter P. Sorokin·James H. Glownia
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Abstract

The near UV spectra of OB stars in our galaxy are often dominated by a very broad extinction band peaking at ~2175 Angstroms. Forty years after its discovery, the origin of this band remains unknown, although interstellar dust particles are generally assumed to be the carriers. Here we report that two-photon absorption by hydrogen molecules in gaseous clouds enveloping OB stars can lead to a band peaking at ~2175 Angstroms. We present astronomical spectral evidence supporting our proposal that this nonlinear absorption mechanism accounts for the lambda2175 feature.

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Peter P. Sorokin, James H. Glownia. 2006-08-03. Two-Photon Absorption by Hydrogen Molecules: Origin of the 2175 Angstrom Astronomical Band?. https://arxiv.org/abs/astro-ph/0608092

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