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Project Progress

We commissioned and calibrated a novel ultra high vacuum surface scattering machine to investigate the formation of astrobiologically important molecules in the interstellar medium, and in our solar system. We are simulating the effects of cosmic radiation on interstellar grains in the interstellar medium to produce new chemical species. Thus, the basic premise of our experimental set-up is to mimic the conditions these grains will be under as realistically as possible.

This machine consists of a stainless steel cylinder; a 12’‘ CF flange serves as the lid of the chamber and holds a centered, differentially pumped feedthrough. This construction enables an attached closed cycle helium refrigerator, and the target to rotate horizontally 360°.Gases are deposited on a cold finger made of a silver mono crystal attached to the 10K cold head. The temperature of the crystal is precisely controllable within a range of 10-350K, mimicking the temperatures expected in the interstellar medium. A magnetically suspended turbomolecular pump backed by an oil free scroll pump is mounted at the bottom of the chamber; this setup generates absolutely oil-free ultra high vacua; so far vacua down to 8 × 10 ^-11 torr have been reached. Gas mixtures are prepared in a mixing chamber. The mixture is introduced via a gas deposition system into the main chamber. A linear transfer mechanism brings the capillary array a few millimeters from the cooled sample substrate. Homogeneous condensation of the mixture provides ice layers of defined crystal structures and reproducible known thickness down to a few tens of nanometers without contamination.

This experimental setup provides reproducible experimental conditions necessary to extract mechanisms leading to the formation of molecules in the solid state upon charged particles, atomic, and photon interaction with extraterrestrial ices. With this machine, electron and ion beams of well-defined kinetic energy and composition can be generated. The modular design of the sources makes it feasible to also incorporate a tunable ultraviolet (UV) photon source in future experiments. During the experiments, after the gas has been deposited to the silver target, the target can be rotated so that an Fourier transform infrared ( FTIR) spectrometer can monitor the chemical modifications of the target in situ by an FTIR spectrometer in the spectral region of 6000-500 cm^{-1 > via absorption-reflection-absorption. Gas species can also be detected via the quadrupole mass spectrometer during an experiment. The sensitivity of this is enhanced by a factor of 100 compared to currently operating machines worldwide.}

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