First General Meeting in Prague, May 25 - 29, 2015The study of carbon chains type Cn and their ions has been attracted a significant effort due to their connection with the astrophysical observations, because pure carbon chains are abundant species in several sources such as the carbon rich circumstellar envelopes. In addition, they can play important roles in the reactivity of large systems containing carbon atoms. Carbon molecules have been considered responsible of the Diffuse Interstellar Bands (DIBs) [1]. Small chains are building blocks of larger species such as the fullerenes and the PAHs.
In spite of their astrophysical relevance, few bare chains have been observed in gas phase extraterrestrial sources. The shortest chain C2, was the first detected, followed by C3 and the linear-C5 [2-3]. Detections were performed through the analysis of Infra-Red active vibrational excitations or through their electronic transitions because they present a zero dipole moment.
All the Cn chains present a large number of isomers, however, in this work we focus on the linear ones. The large stability of charged linear chains was used as argument to predict the presence of anions in the interstellar medium. We present computed molecular properties calculated using highly correlated ab initio methods (CCSD(T)-F12, MRCI/CASSCF). We determine structures, infrared frequencies and excitations energies to the lowest electronic states and electron affinities of the small chains type Cn (n=3,4,5,6,7). Special attention is given to the anions which relevance for reactivity is evident. Non-adiabatic effects and spin-orbit effects will be predicted.Peer Reviewe
