Some important molecules detected in the interstellar medium

In the cold parts of the interstellar medium there are icy dust grains. These particles are important because they may act as catalysts. 

The interstellar medium may also appear as dark clouds that absorb starlight. The densities are several 10 particles cm . In such clouds polycyclic aromatic hydrocarbons (PAHs), fullerenes, carbon-chains, diamonds etc. are found. 

Some of the molecules that have been detected in the interstellar medium are listed in Table 7.1. This table is only an incomplete sample of the long list of molecules that have been detected. 

It is believed that pristine water is formed and grows on the surface of icy dust grains in dark interstellar clouds. This has been proven experimentally by atomic beams of oxygen and deuterium aimed at a porous water ice substrate (H2O) held at 10 K 

There are astronomical observations that provided big puzzles to their interpretation. For example emissions that correspond to surface temperatures of the objects of up to 10 K. These emissions can only be explained by Maser emission. 

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Table 7.1 Some important molecules detected in the interstellar medium...

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