Matrix isolation in laboratory astrochemistry: state-of-the-art, implications and perspective

Recent progress in observational astronomy and astrophysics has stimulated intensive laboratory studies aimed at elucidating the mechanisms of evolution of molecular matter in interstellar space and various space objects. One of the most intriguing and rapidly developing areas of these studies is the so-called “cold astrochemistry” devoted to the complex processes occurring in astrophysical ices. In this context, the matrix isolation technique (known for decades) is a very useful approach for both interpreting the results of astrophysical observations and verifying possible mechanisms of key astrochemical processes. This review outlines the most important results of recent studies using the matrix isolation technique. In fact, the results of these studies contribute to “cold” astrochemistry in two main aspects: (i) spectroscopy of astrochemically important molecules, ions and radicals stabilized in cryogenic matrices; (ii) experimental modeling of mechanisms of radiation-induced and “in dark” chemical reactions occurring in “cold” space environments (interstellar, cometary and planetary ices). In the first aspect, special attention is paid to new spectroscopic data obtained using various methods (electronic and vibrational absorption spectroscopy, electron paramagnetic resonance spectroscopy). In the second aspect, we consider the chemical effects resulting from both direct excitation of isolated molecules and the transfer of energy initially absorbed by the medium. Special attention has been paid to recent studies of spectroscopic characteristics and radiation-induced evolution of matrix-isolated weak intermolecular complexes, which can be considered “building blocks” for cold synthesis of complex molecules in the absence of diffusion mobility. In addition, we consider the use of matrix isolation for the studies of low-temperature chemical reactions “in dark” involving atoms and highly reactive intermediates, which can occur in cold space environments. In the final part, we briefly discuss the applicability of the results of matrix isolation experiments for interpretation of the mechanisms in molecular ices and highlight the prospects of this field. The review can also be useful for specialists in various aspects of chemistry and chemical physics (radiation chemistry, photochemistry, molecular spectroscopy, low-temperature chemistry). The bibliography includes 379 references.