OSIC

In one of the areas within the research field of astrobiology one studies the existence and formation of complex molecules both by astronomical observation but also in laboratory model chambers. The setup for infrared-spectroscopy of "Organics under Simulated Interstellar Conditions" (OSIC) is such a model chamber dedicated to the study of carbonaceous material in ultra-high vacuum at low temperature and under UV irradiation.
The setup consists of an octagonal vacuum chamber evacuated by a pumping system equipped with a cold trap. A rotatable (infrared transparent) CsI substrate is thermally connected to a closed cycle helium refrigerator and suspended in the center of the vacuum chamber (see Figure 2). The substrate can be rotated to face alternatively;

  1. The deposition system consisting of a gas inlet tube and a sublimation oven operating at a maximum temperature of 825 Kelvin.
  2. A hydrogen flow UV lamp connected to a microwave generator that produces Lyman alpha photons with an energy of 10.6 eV.
  3. A Fourier Transform Infrared Spectrometer with a spectral range of 6000-400 cm-1.

Figure 1 is an overview of the OSIC setup. The experimental chamber is placed inside the optical bench of the infrared spectrometer. The setup can be slided out of the spectrometer for easy access to the experimental chamber.


Figure 1: OSIC setup.

Figure 2 provides a schematic of the experimental chamber. The three stages of a typical experiment are depicted. During the sublimation configuration a flow of argon (or another matrix gas) is frozen onto the cold (10 Kelvin) substrate. By simultaneously subliming a solid organic sample, a matrix containing isolated organic molecules is formed. The composition of the matrix is measured by FTIR-spectroscopy. Energetic processing of the sample by vacuum UV radiation drives chemical and photochemical reactions in the samples. The results of these reactions are than measured by spectroscopy. The substrate temperature can be set to a value between 12 K - 273 K.

 
Figure 2: OSIC chamber configuration.

After cooling the substrate to 10 Kelvin, solid organic material is sublimed and deposited on the cold substrate by a sublimation oven. By simultaneously flowing a stream of argon while the oven is operating, the organic material can be frozen into different matrices (i.e. noble gases, water, carbonmonoxide, carbondioxide, oxygen etc.). More complex matrices can be obtained by mixing different gases on a glass manifold. This manifold is available in our laboratory and operates at an average pressure of 5 * 10-5 mbar. This allows infrared spectroscopic studies of organic materials under simulated interstellar conditions. By irradiating the samples with high and low energy UV photons we can determine the photo-stability of the sample molecules.
The cryostat allows the selection of a substrate temperature between 12 Kelvin and 273 Kelvin with an accuracy of 1 Kelvin. By combining the laboratory results with astronomical observations we can obtain information on the abundance, type of carbon carriers and distribution of carbon based materials in our universe.

The OSIC facilities is open for collaborative studies with the university Leiden. When you are interested to perform a series of (pilot) studies using the OSIC you are invited to contact us and discuss various possibilities for collaborative studies. You may also directly send an experiment proposal either to DESC or respond to one of the international 'Announcements of Opportunities' (AO) as are in general annually issued by the European Space Agency (ESA) or other space agencies. You may also apply via an unsolicited proposal to ESA via the 'fast track' Continuously Open Research Announcements. You may contact us when you need any support for this. Dutch scientists may also apply nationally via a NSO-NWO proposal. An additional copy of the proposal has to be provided to DESC for technical and operational evaluations.

OSIC Detailed description

  • The system is made of a stainless steel vacuum system and sealed with aluminum and rubber O-rings. A diffusion pump and rotary roughing pump are mounted on the setup, separated by a liquid nitrogen cold trap.
  • System pressure at room temperature is 4.0-5.0 * 10-8 mbar.
  • There are four ports in the vacuum chamber, 2 ports are sealed with infrared transparent KBr windows, 1 port is sealed with UV transparent MgF2 and 1 port is equipped with a sublimation oven.
  • The substrate holder is thermally connected to the cold tip of the closed-cycle helium refrigerator and can be fitted with CsI, Aluminum and IR fused silica substrate disks.
  • The temperature of the closed cycle Helium refrigerator system can be set to any value in the interval between 12 - 273 Kelvin with a resolution of 1 Kelvin.
  • To control the matrix to sample ratio, a flow valve is mounted on the gas inlet port.
    The hydrogen discharge lamp emits a flux of 1 * 1015 photons.cm-2.s-1 of photons with energy ~ 10.6 eV.
  • A narrow quartz tube is filled with organic sample and mounted in the sublimation oven.
  • The sublimation device allows selectable temperatures between room temperature and 550 degrees Celsius with a resolution of approximately 2 degrees Celsius.
  • A thermocouple for temperature reading is fitted inside the sublimation device at the level of the quartz sample tube.

The OSIC setup is located in the Sackler Laboratory for Astrophysics at Leiden University. It was built in dedication of the "ORGANIC" long duration exposure experiment on the SEBA expose pallet on the International Space Station and is funded by SRON grand MG-049 titled "Evolution of Organic Matter in Space". The system is operated by Prof. P. Ehrenfreund and R. Ruiterkamp.
More links to astrobiology related web sites are found at the Link page.

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