The singlet and triplet states of HF2+: a theoretical study

We study the singlet and triplet states of HF2+ at the B3LYP, BHandH, BHand HLYP, MP2, MP3, MP4 and QCISD(T) levels of theory with the 6-311++G(2DF,2PD ) basis set. We report geometries, vibrational frequencies and vertical exc itation energies. We find that the ground state of HF2+ is the C-s HFF+ sin glet with r(F-F) = 1.444, r(H-F) = 0.980 Angstrom and alpha = 101.96 degree s; omega(1) = 857, omega(2) = 1145 and omega(3) = 3320 cm(-1), For the trip let state, there are two stable structures: the C-s HFF+ triplet (T-e = 0.7 9 eV) with r(F-F) = 1.799, r(H-F) = 0.962 Angstrom and alpha =102.53 degree s; omega(1) = 543, omega(2) = 734 and omega(3) = 3530 cm(-1) and the C-infi nity 1, FHF+ triplet (T-e = 0.92 eV) with r(H-F) = 1.179 Angstrom; omega(1) = 544, omega(2) = 900 and omega(3) = 1418 (-1). (C) 2000 Elsevier Science B.V. All rights reserved.