IS INTERSTELLAR DETECTION OF HIGHER MEMBERS OF THE LINEAR RADICALS CNCH AND CNN FEASIBLE

Rotational constants and dipole moments for linear-chain radicals C(n)CH and C(n)N are estimated using a combination of ab initio molecular orbital calculations and observed data on the starting members of the series. C(n)CH with n = 0-5 have been observed by radioastronomy in carbon-rich interstellar clouds; higher members of the series have 2-PI ground states with large dipole moments and are strong candidates for observation. CN and C3N have also been observed by radioastronomy; higher members of the series, with the possible exception of C5N, have 2-PI ground states with near-zero dipole moments making their interstellar detection hopeless under present observational conditions. C5N can be a strong candidate only if it has a 2-SIGMA ground state, and our best computations so far indicate that this is not the case.