The HO+2 molecular ion. Geometrical structure and vibrational frequencies

Abstract

The equilibrium geometry and harmonic vibrational frequencies of HO+2 have been predicted at seven distinct levels of ab initio theory. In this regard, self-consistent-field (SCF) and configuration interaction (CI) methods were used in conjunction with double zeta (DZ), double zeta plus polarization (DZ+P), and extended basis sets of contracted Gaussian functions. The molecular structure of HO+2 predicted at the DZ+P CI level of theory is re(H–O) =1.005 Å, re(O–O) =1.239 Å, θe(HOO) =111.5°, compared to the experimental structure of neutral HO2, r0(H–O)=0.977 Å, r0(O–O)=1.334 Å, θ0(HOO)=104.2°. Anharmonic vibrational frequencies were also predicted at four different levels of theory, with the DZ+P CI results being ν1=3204 cm−1, ν2=1572 cm−1, ν3=1144 cm−1. For comparison, the observed fundamentals for the neutral HO2 molecule are ν1=3436 cm−1, ν2=1392 cm−1, and ν3=1098 cm−1.