Optical Parametric Oscillator (OPO)

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The laboratory astrophysics group (AG Schlemmer) develops new methods of molecule spectroscopy. Various radiation sources are used for this purpose. One unique field of research concerns the action spectroscopy of trapped molecular ions which led to publications in Science, Nature, Nature Chemistry and Nature Review Physics. With the help of the requested cw OPO new two color experiments become possible. One (existing) color is used to address a molecular ion such that they are reacting to products which can be distinguished from the parent ion in our ion trap instruments. Since onle y finite ensemble of ions is stored in these experients the fraction of reacting ions and non-reacting ions can be determined and a branching ratio of different parent ions can be measured. Thus structural isomers, conformers and even nuclear spin isomers can be isolated. Via the second color also the other species can be addressed in the same experiment. So they leave the parent ensemble as well. In an experiment with two isomers this could lead to the loss of all parent species from the ensemble. However, when a neutral collision partner is added to the trap inbetween the periods when the light is depleting the ensemble, isomer conversion will happen and not all reactant molecules will be converted. As a result the rate for such a conversion process can be determined. Such fundamental processes, e.g., nuclear spin converion via chemical reactions, can be crucial for the process of star formation out of a molecular cloud. The OPO proposed here will make such experiments possible for the first time. Distinguishing isomers is a topic with large potential for applications (analytics). Two color experiments will also enable to unfold spectra of floppy molecules without a regular structure, e.g. the enigmatic protonated methane molecule.