Articles you may be interested inStudies on the structure, stability, and spectral signatures of hydride ion-water clusters J. Chem. Phys. 135, 214308 (2011); 10.1063/1.3663708 Ion-water interaction potentials in the semimicroscopic model Structures and energetics of monovalent ion-water microclusters. II. Thermal phenomena J. Chem. Phys. 89, 7492 (1988); 10.1063/1.455282 Structures and energetics of monovalent ion-water microclusters
Photofragmentation studies are described for mass-selected transition metal cluster ions cooled in a supersonic expansion. Examples of the spectral utility of this technique are presented in the cases ofNi/ and Nb/ for which well resolved vibronic bands have been recorded by monitoring fragment yield as a function of dissociation laser wavelength. For larger, more complicated metal clusters the absorption spectrum is far too congested and perturbed for analysis, but photodissociation can r~veal the thresholds and time scales of various fragmentation pathways. The order of the absorptlon event leading to dissociation is found from the extent of fragmentation as a function oflaser fluence. Using this method, the one-photon dissociation threshold of Fe + is found to lie between 2.43 and 2.92 eV, which determines the binding energy of this transiti;n ~et~ dimer cation. Combined with previous ionization potential measurements this places the btndmg energy ofthe Fe 2 neutral between 0.83 and 1.32 eV. Similarly, the threshold for dissociat~on .ofFe 3 + into Fe2+ + Fe was found to lie between 1.17 and 2.18 eV, placing the Fe3 ne.utral bmdmg energy between 1.27 and 2.38 e V. For all transition metal clusters measured (Fe x , Nix, and Nb x with x between 2 and 10) the primary one-photon fragmentation pathway was always found to be loss of a single metal atom from the cluster. Far more accurate measures of these dissociation thresholds should be possible with more extensive measurements of cold cluster ion photodissociation as a function of wavelength. Arguments are presented to the effect that these dissociation thresholds should generally provide valid measures of the true binding energies of transition metal clusters. 3078
Photofragmentation of the V(OCO)+ molecular ion in the visible shows sharp resonant absorption features and two distinct dissociation pathways: V+(OCO)+→V++CO2 and V(OCO)+→VO++CO. The photodissociation excitation spectrum reveals two low frequency vibrational modes in the upper state of this molecule at 105 and 196 cm−1. This spectrum indicates that the same photoexcited state in V(OCO)+ is the precursor to both V+ and VO+ products. The branching ratio for VO+/V+ production depends on the excitation energy and upper state vibrational mode. An estimate of the barrier to the production of VO+ of 13 000 cm−1 (37 kcal/mole) above the ground state of V(OCO)+ is made from this data.
The electrostatic complex of Co+ with a single N2 molecule is studied by optical excitation of the metal ion.Vibrational structures of such electronic transitions show excited state progressions of the complex modes.A single far-red transition shows little geometry change upon excitation and displays the rotational contour of a nonlinear complex. Yellow transitions show vibrational structure indicative of a gross geometry change with progressions in both stretching and rocking modes. This suggests that CON*+ possesses a "T"-shaped ground state and both linear and nonlinear excited states. A particular linear upper state, the B state, is characterized vibrationally with a typical metal-ligand stretching frequency (140 cm-') but a rather flaccid rocking frequency (14 cm-l). The geometry change upon 3d74s -3d8 excitation of the Co+ ion in this complex is discussed in terms of a simple model potential which includes both electrostatic and inductive components.
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