Electronic, Structural, and Hyperfine Interaction Investigations on Rydberg Molecules: NH4, OH3, and FH2

The geometrical structures of NH 4 and OH 3 were optimized at the MP2 level with the aug-cc-pvdz, aug-cc-pvtz, and aug-cc-pvqz basis set plus s-type diffuse functions. The adiabatic ionization potential, barrier height, and dissociation energy of NH 4 and OH 3 were calculated with the above basis set series and were extrapolated to the infinite basis set limit. The theoretical ionization potential of NH 4 was in very good agreement with the experimental value. The N−H bond lengths of NH 4 and NH 4 + at the infinite basis set limit were obtained by parabolic interpolation around the equilibrium point. FH 2 was optimized at the UHF, B3LYP, and MP2 levels. However, only a dissociated ground state was found. The potential energy curves for dissociation of the above molecules were calculated with MP2. The relative stabilities of these molecules and their isotopic counterparts are discussed. Theoretical hyperfine calculations were performed in the gas phase as well as in a neon matrix for NH 4 and OH 3 with a single-reference configuration interaction method (CI) and multireference single- and double-excitation methods (MRSD), respectively. For FH 2, only gas phase calculations are carried out. The contours of the singly occupied orbitals of NH 4 and OH 3 in the gas phase and in the neon matrix are plotted to show their s-type character.