Theoretical prediction of new dipole-bound singlet states for anions of interstellar interest

Anions that exhibit dipole-bound singlet states have been proposed as a potential class of molecules that may be identified in the interstellar medium. Using high-level coupled cluster theory, we have computed the dipole moments, electron binding energies, and excited states of 14 neutral radicals and their corresponding closed-shell anions. We have calibrated our methods against experimental data for CH2CN- and CH2CHO- and demonstrated that coupled cluster theory can closely reproduce experimental dipole moments, electron binding energies, and excitation energies. Using these same methods, we predict the existence of dipole-bound excited states for six of the 14 previously unknown anions, including CH2SiN-, SiH2CN-, CH2SiHO-, SiN-, CCOH-, and HCCO-. In addition, we predict the existence of a valence-bound excited state of CH2SiN- with an excitation wavelength near 589 nm. (C) 2011 American Institute of Physics. [doi:10.1063/1.3576053]