An ab initio molecular orbital study of the argon hydride molecule-ions, ArH+ and ArD+, at the MP4(SDQ)/6-311++G(3df, 3dp) level. I. The dipole moment, charge distribution, energy levels, internuclear distance and potential energy of the X1Σ+ ground

The X1Σ+ state of the 40Ar1H+ and 40Ar2D+ was explored with an ab initio molecular orbital (MO) study (MP4, basis set 6-311++G(3df, 3pd), followed with SDQ): ETotal=−527.182 771 62 hartree at Re=1.2767 Å (Exp. 1.280 3730(11)); De=33 509.189 cm−1; μ=1.9283 D. The potential energy (PE) follows a Morse curve with r2=0.9993. Vibrational term values are G0(ArH+)=1374.95 (ArD+: 964.83) cm−1 and G1(ArH+)=4038.13 (ArD+: 2788.47) cm−1. Rotational constant B=315.406 897 GHz for 40Ar1H+ and 161.70 GHz for 40Ar2D+ (Exp. 158.702 3259(55) GHz). The energy level diagram and the electron density contours are discussed.