Cold Chemistry in Space and Laboratory
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Stephan Schlemmer
Univ. of Cologne
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Molecules are tracers of specific eras of star formation. In cold molecular clouds only hydrogen bearing species remain in the gas phase while most other species are frozen out on grains. Among these gas phase species are H3+ and its deuterated isotopologues, H2D+, D2H+ and D3+. Their relative abundance, e.g. H2D+/H3+, and their ortho to para ratios (OPRs), e.g. the OPR of H2D+, are related to the OPR of H2, to the temperature of the environment and to the age of the cloud. I will show how the relevant ratios can be determined in the laboratory. In particular I will present the spectroscopic capabilities of our cold ion trap experiments providing the THz transition frequencies which enabled the recent, first observation of p-H2D+ by the GREAT instrument aboard SOFIA. As a result the observed OPR of H2D+ could be used to delineate the temporal evolution of the observed cloud core which forms sun-like stars. This is one example of how our laboratory work on cold chemistry can reveal parts of the cosmic cycle of matter.

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