Potential energy and dipole moment surfaces of HCO− for the search of H− in the interstellar medium

Abstract

Potential energy and permanent dipole moment surfaces of the electronic ground state of formyl negative ion HCO(-) are determined for a large number of geometries using the coupled-cluster theory with single and double and perturbative treatment of triple excitations ab initio method with a large basis set. The obtained data are used to construct interpolated surfaces, which are extended analytically to the region of large separations between CO and H(-) with the multipole expansion approach. We have calculated the energy of the lowest rovibrational levels of HCO(-) that should guide the spectroscopic characterization of HCO(-) in laboratory experiments. The study can also help to detect HCO(-) in the cold and dense regions of the interstellar medium where the anion could be formed through the association of abundant CO with still unobserved H(-).