Speaker
Description
Dust grains are important components of the interstellar medium (ISM). Their surfaces are typically covered by icy mantles formed through the condensation of gas-phase species of the ISM. Upon exposure to external irradiation, such as cosmic rays, chemical reactions can be initiated within these ice layers. [1] These reactions lead to the formation of new chemical species, some of which can subsequently sublime from the condensed phase into the gas phase, thereby altering the original composition of the gaseous ISM. [1,2]
Interstellar ice analogs containing molecules present in the ISM, including methanol (CH3OH), ethanol (CH3CH2OH), methyl amine (CH3NH2), and ammonia (NH3), have been experimentally studied using the VIZSLA (Versatile Ice Zigzag Sublimation Setup for Laboratory Astrochemistry) setup. [3] First, the ices were condensed onto a cold surface. Then, to simulate the effects of cosmic-ray irradiation, the ices were bombarded with 5 keV electrons. After that, the irradiated samples were heated in a controlled manner. During the temperature-programmed heating, two distinct experiments were performed for each sample. In the first, spectral changes of the processed ices were monitored throughout the entire heating process. In the second, species sublimating from the ice were allowed to recondense onto a second substrate. During this recondensation process, the matrix-isolation technique was employed, enabling the more sensitive identification of the recondensed species, i.e., the molecules sublimating from the ice during the temperature-programmed desorption.
The experiments showed the formation of several reaction products both in electron bombarded CH3OH:CH3NH2 and CH3CH2OH:NH3 astrophysical ice analogs. Collectively, the studied processes contribute to our understanding on the chemical evolution of the ISM and demonstrates that interstellar ices are an important source of chemical complexity in space.
[1] E. F. van Dishoeck, G. A. Blake, Annu. Rev. Astron. Astrophys., 36 (1998), 317.
[2] W. D. Watson, E. E. Salpeter, Astrophys. J., 174 (1972), 321.
[3] Bazsó, G.; et al. Rev. Sci. Instrum. 2021, 92(12), 124104-124143.
Summary
Chemical processes potentially occurring in the ISM have been experimentally investigated using the VIZSLA setup. Studies of astrophysical ice analogs containing methanol, ethanol, methylamine, and ammonia have shown that electron bombardment, used to simulate the cosmic ray irradiation of the ISM, induces a variety of chemical reactions, leading to the formation of several organic compounds and to the increase of the chemical complexity of the Universe.