Irradiated methane ice forms heavy hydrocarbons


Irradiated methane ice forms heavy hydrocarbons

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  • Published: Jun 10, 2013
  • Author: Steve Down
  • Channels: Atomic / Base Peak / X-ray Spectrometry / Proteomics / Infrared Spectroscopy / MRI Spectroscopy / Chemometrics & Informatics / UV/Vis Spectroscopy / Raman / NMR Knowledge Base

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Methane has been found as ice on several planets in our solar system, as well as on stellar objects, but its structure is a mystery despite the efforts of many research groups. It doesn’t remain as methane but is transformed by ionising radiation like charged particles and high-energy photons into a number of products. So far, hydrocarbons like acetylene, ethane and propane have been identified but scientists in Hawaii have just gone much further.

In a set of earthly experiments, Brant Jones and Ralf Kaiser from the University of Hawaii, Manoa, have found hydrocarbons containing up to 22 carbon atoms. Writing in The Journal of Physical Chemistry Letters, they tell how they froze methane on a mirror within an ultrahigh vacuum chamber and bombarded it with electrons. When the chamber was warmed slowly, the hydrocarbons that sublimed were ionised gently by photoionisation and analysed by reflectron time-of-flight mass spectrometry.

More than 50 alkanes, alkenes, alkadienes and alkynes were detected, although the specific structures could not be determined. Hydrocarbons this size have never been seen before in methane ice. The results are particularly timely for the NASA New Horizons mission loaded with scientific instruments on its way to Pluto, where it is scheduled to fly past in July 2015.

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