Theoretical rotational constants and IR signatures of protonated polycarbon dioxides OCnO

This study considers the possibility of astronomical detection of members of the CnO2H series; these are possible tracers of the parent polycarbon dioxide molecules, OCnO. Direct radio detection of these molecules is not possible owing to non existent or too small dipole moments. The structures of all stable isomers were determined according to protonation sites. Rotational constants and dipole moments for the most stable protonated species were predicted by molecular electronic structure calculations and the error bar was estimated using a combination of observed data on the starting member of the series, HOCO+, and the closely related family of polycarbon monoxides, CnO. These molecular constants, accurate to within 0.2%, along with the calculated IR spectra, should assist in the identification of these species in the laboratory and in tentative assignments of interstellar lines.