Polarizability of isomeric and related interstellar compounds in the aspect of their abundance

Currently, about 100 carbon-containing molecules have been detected in interstellar and circumstellar environments, and this list includes isomeric substances. In most cases, the minimum energy principle is able to explain the ratio of abundances of the isomeric compounds but in some cases is not. Trying to rationalize the questions unsolved within the energetic approach, we have theoretically studied the polarizability of isomeric and related compounds detected or proposed in interstellar conditions. As we found, in general both energy and polarizability provide the consistent estimates for the ratio of the isomers (e.g., for the isomers having generic formulae CHO, CHN, C₃H, C₃H₂, CHNO, C₂H₃N, C₂H₆O, etc.). In the case of the C₄H₃N isomers, the most abundant isomer (cyanoallene) is not the most stable but the least polarizable that is in a good agreement with relevant experimental study. We assume that the efficiency of the use of polarizability is due to its relevance to the molecules’ response to the external electric fields, i.e., more polarizable molecules are more responsive, more reactive, and, hence, less abundant. Further, we have analyzed the polarizabilities of polycyclic aromatic hydrocarbons, fullerene hydrides (fulleranes), polyynes, and their derivatives with respect to their possible detection under interstellar conditions.