Experiments
The ISEAge UHV setup makes it possible to recreate in laboratory conditions ices composed of molecules observed in the interstellar medium and to study their properties, such as the shapes and intensities of absorption bands, reaction rate constants, and adsorption energies, using infrared spectroscopy and mass spectrometry.
The setup is a complex of sophisticated equipment: its most essential components, in addition to the main ultra-high vacuum (UHV) chamber, include an infrared spectrometer, a mass spectrometer, turbomolecular and fore-vacuum pumps, as well as a variety of sensors for measuring temperature and pressure. At the center of the chamber is a germanium substrate, transparent to infrared radiation, whose temperature can reach as low as 6.5 K due to the operation of a helium cryostat. It is this substrate that mimics the surface of silicate or carbonaceous particles on which ices form in the interstellar medium.
The dosing line is of particular importance: all studied substances, previously converted into the gas phase, pass through it before entering the main chamber. The dosing line consists of numerous metal tubes and reservoirs interconnected by vacuum flanges. The airtightness of all connections ensures the purity of the substances under study. In the dosing line, the gases undergo purification and are stored throughout the experiment.
The prepared substances are introduced into the main chamber through a pair of leak valves. At the same time, partial condensation of the gases occurs on the cooled substrate, while infrared spectra are simultaneously recorded. The molecules are deposited uniformly on both sides of the substrate, ensuring that the ice grows perpendicular to the infrared beam and, consequently, preventing any additional distortions in the obtained spectra.
The setup is a complex of sophisticated equipment: its most essential components, in addition to the main ultra-high vacuum (UHV) chamber, include an infrared spectrometer, a mass spectrometer, turbomolecular and fore-vacuum pumps, as well as a variety of sensors for measuring temperature and pressure. At the center of the chamber is a germanium substrate, transparent to infrared radiation, whose temperature can reach as low as 6.5 K due to the operation of a helium cryostat. It is this substrate that mimics the surface of silicate or carbonaceous particles on which ices form in the interstellar medium.
The dosing line is of particular importance: all studied substances, previously converted into the gas phase, pass through it before entering the main chamber. The dosing line consists of numerous metal tubes and reservoirs interconnected by vacuum flanges. The airtightness of all connections ensures the purity of the substances under study. In the dosing line, the gases undergo purification and are stored throughout the experiment.
The prepared substances are introduced into the main chamber through a pair of leak valves. At the same time, partial condensation of the gases occurs on the cooled substrate, while infrared spectra are simultaneously recorded. The molecules are deposited uniformly on both sides of the substrate, ensuring that the ice grows perpendicular to the infrared beam and, consequently, preventing any additional distortions in the obtained spectra.
Experiments
Transmission IR spectroscopy of pure and multicomponent ices
TPD experiments with pure and multicomponent ices
Study of chemical reactions in the ice phase at various temperatures
The essence of most experiments consists in obtaining IR spectra which will subsequently be compared with spectra obtained from spacecraft. These data are necessary for studying physical and chemical processes occurring in laboratory ices. The research results are compared with data obtained from real ices.
Molecules are deposited onto the cooled germanium substrate simultaneously with spectrum recording: in this way all stages of ice formation are fixed and changes in absorption band shapes are observed depending on the number of molecules in the line of sight of the IR spectrometer. The purity of deposited substances is controlled using a quadrupole mass spectrometer. It is also used to determine the pressures at which deposition should be performed. Based on spectrometer readings, the approximate ice thickness and number of molecules lying in the path of the infrared beam can be determined.
Molecules are deposited onto the cooled germanium substrate simultaneously with spectrum recording: in this way all stages of ice formation are fixed and changes in absorption band shapes are observed depending on the number of molecules in the line of sight of the IR spectrometer. The purity of deposited substances is controlled using a quadrupole mass spectrometer. It is also used to determine the pressures at which deposition should be performed. Based on spectrometer readings, the approximate ice thickness and number of molecules lying in the path of the infrared beam can be determined.
Transmission IR spectroscopy of pure and multicomponent ices
Another variant of experiments is temperature-programmed desorption (TPD) — in this case, gradual heating of the substrate and, consequently, evaporation of molecules from its surface occurs. During such research, it becomes possible to determine the adsorption energy and intermolecular interactions of substances. Moreover, during TPD experiments, based on readings from both spectrometers, the temperature dependencies of IR spectra, kinetics of chemical reactions, and phase transitions in ices can be studied.
TPD experiments with pure and multicomponent ices
48 Kuibysheva St., Yekaterinburg, Russia
Research Laboratory
for Astrochemistry UrFU
for Astrochemistry UrFU