Hypervalent molecules of Li3F and Li4F were detected experimentally for the first time. Ionization energies determined by the thermal ionization mass spectrometry were 3.8 +/- 0.2 eV for Li2F, 4.0 +/- 0.2 eV for Li3F and 3.9 +/- 0.2 eV for Li4F. The ionization energies obtained by ab initio calculations support the experimental findings. The lowest energy structures of the LinF (n = 2-4) molecules and their cations were also predicted. (C) 2007 Elsevier B.V. All rights reserved.