New bound electronic states of NH⁺

Abstract

Ab initio MRD-CI electronic structure calculations were carried out on the NH ϩ cation. A basis set of DZ ϩ 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 ϩ , namely, three doublets ( 2 ⌬, 2 ⌺ ϩ , 2 ⌺ ϩ ) and one sextet ( 6 ⌸). A fifth bound electronic state, a quartet ( 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 NOH 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 NH 2ϩ (X 1 ⌺ ϩ ) was also calculated to aid in the discussion of a Rydberg bound state of NH ϩ . It is hoped that the information reported in this article will be helpful in guiding the experimental detection of these species.

Electronic structure of NH+: An ab initio study

“…In Ref. 1 we discussed the AO composition and nature of the eight MOs involved in the description of the five already known and the five new bound states of NH + at various N–H internuclear distances. At the equilibrium distance of NH + (X) 1σ, 2σ, 3σ, 11σ, 1π, and 4π are valence MOs, 4σ is Rydberg, and 9σ is predominantly Rydberg.…”

“…A first, qualitative insight into the electronic structure of NH + can be obtained from MO theory based on Figure 1 and Figure 1 of Ref. 1. These figures enable to infere the most stable electron arrangement of the seven‐electron system as well as the excited arrangements (configurations) giving rise to the lowest manifolds of excited electronic states.…”

“…Conversely, little has been published on the related species NH + . In a recent paper, hereafter referred to as “Paper I” 1, we presented an overview of the theoretical and experimental work published so far on NH + ; therefore, only some of the salient features of this cation are mentioned here.…”

“…The new bound states were reported and discussed separately because of their intrinsic relevance as possible sources of discrete spectral features usually easier to recognize experimentally (as opposed to, e.g., broad, structureless features characteristic of bound–repulsive transitions that are difficult to identify in the spectral baseline). Paper I 1 was, however, just a part of a wider ab initio study of the electronic structure of NH + . In the current contribution we report our results for all computed electronic states of NH + , bound and unbound.…”

Theoretical study on the ion–molecule reaction of NH+ with CH2O

“…Up to now, a large number of experimental and theoretical studies have been performed to investigate its properties [9][10][11][12] and reactions [13]. The observation of NH þ spectrum has long intrigued astronomers [14][15][16]; SCF calculations on the ground (X 2 P) state of this ion was made by Liu and Verhaegen in 1970 [17] and Polák et al [18] studied the potential energy surfaces of the quartet NH þ ( 4 R À ) þ H 2 ( 1 R þ g ) system in 1993.…”