Photodissociation measurements of bond dissociation energies: D0(Al 2-Al), D0(TiO +-Mn), and D0(V 2+-V)

• Published in: International journal of mass spectrometry 2001-02, Vol.204 (1), p.143-157
• Main Authors: Fu, Zhenwen, Russon, Larry M., Morse, Michael D., Armentrout, P.B.
• Format: Article
• Language: English
• Subjects: Bond energy; Dissociation energy; Predissociation
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/S1387-3806(00)00331-6

The bond dissociation energies D 0(Al 2–Al) = 2.701(5), D 0(TiO +–Mn) = 1.7629(12), and D 0(V 2 +–V) = 2.323(1) eV have been measured from the sudden onset of predissociation in the photodissociation spectra of Al 3, TiOMn +, and V 3 +. For Al 3, the predissociation threshold was observed in a spectrum arising from the metastable 4 A 2 state (in C 2 v symmetry), and the value of D 0(Al 2–Al) = 2.701(5) eV was obtained by adding the energy of the 4 A 2 state to the measured predissociation threshold. For TiOMn +, there is currently no evidence that the predissociation threshold arises from a metastable excited electronic state; nor is there evidence that dissociation at the ground separated fragment limit fails to occur. Therefore, the predissociation threshold is taken to be the bond dissociation energy for this molecule. For V 3 +, the measured predissociation threshold occurs 0.32 eV above the collision-induced dissociation (CID) measurement. Based in part on a theoretically suggested 9 A ″ 2 ground state for V 3 +, it is suggested that predissociation of V 3 + occurs efficiently only after the V (3 d 44 s 1, 6 D 1/2) + V 2 + ( X 4Σ g,1/2 −) separated fragment limit is exceeded in energy. Making a correction for the energy of this excited separated fragment limit then brings the photodissociation measurement into agreement with the CID result, and allows the bond energy to be determined as D 0(V 2 +–V) = 2.323(1) eV.