New bound electronic states of NH+

Ab initio MRD-CI electronic structure calculations were carried out on the NH+ cation. A basis set of DZ + POL quality augmented with Rydberg and bond functions was employed, together with an extensive treatment of electron correlation. We find four new bound electronic states of NH+, namely, three doublets ((2)Delta, (2)Sigma(+), (2)Sigma(+)) and one sextet ((II)-I-6). A fifth bound electronic state, a quartet ((II)-I-4) that was reported schematically in an early SCF study (Liu, H. P. D.; Verhaegen, G. J Chem Phys 1970, 53(2), 735), is calculated for the first time over a wide range of N-H distances. Electronic energies, potential energy curves, and spectroscopic constants are reported for these five states. Vertical and adiabatic excitation and ionization energies are reported, as well as vertical de-excitation energies for emission from the novel states to lower-lying bound states. The potential energy curve of NH2+ (X1Sigma(+)) was also calculated to aid in the discussion of a Rydberg bound state of NH+. It is hoped that the information reported in this article will be helpful in guiding the experimental detection of these species. (C) 2004 Wiley Periodicals, Inc.