Abstract
This thesis deals with the process of molecular ions formation in interstellar space, which played an important role in the early Universe. A large part of the work focuses on the theoretical study of quantum dynamics of the process of radiative association pre- dominantly induced by dipole transitions.
The effect of quadrupole transitions on the radiative association have also been taken into account, which has been studied for the first time. Furthermore, spectroscopic characteristics of rovibronic transitions of selected di- atomic ions for the study of cosmological variability of fundamental constants were determined.
The main outcomes of the thesis include the characterization of depopulation of metastable levels He (23S) and He (21S) due to radiative collisions with hydrogen, helium and lithium ions, i. e. He + A+ RIGHTWARDS ARROW HeA+ + hν.
Within the study quantum dynamics calculations were carried out using a fully quan- tal approach. Studied spontaneous and stimulated processes on a specific spin manifold were characterized by energy-dependent cross sections and temperature-dependent rate coefficients.
Compared to previous published works by other authors highly excited electronic states are considered. The results showed that a) the spontaneous radiative association contributes signi ficantly to the depopulation of metastable helium atoms in planetary nebulae; b) the stimulation of radiative association by black-body background radiation has a significant influence only at relatively low temperatures and only on the processes, where the energies of emitted photons are rather small. keywords: molecular processes, atomic processes, radiative association, metastable helium, adiabatic approximation, rates of formation, molecular ions, astrochemistry, interstellar environment