FO+ and FO ab initio vibrational constants

The potential energy surfaces for both FO neutral and cation were calculated at CCSD(T)/cc-pVTZ (sixty basis functions). From these surfaces the vibrational levels were obtained using the Fourier grid Hamiltonian method. The spectroscopic constant obtained are: FO ωe = 1072 cm−1 and ωexe = 12 cm−1, FO+ ωe = 1331 cm−1 and ωexe = 11 cm−1. The same calculations on the isoelectronic (to FO+)O2 molecule yield an ωe within 1% of the spectroscopically determined value and within 20% for ωexe. The Franck-Condon factors were calculated for transitions from the lowest two level of FO to FO+. The peak intensity for the transition FO+(X3Σ−) ← FO(X2Π ν″ = 0) occurs at ν′ = 2.