The electronic spectra of Co(+)(H(2)O), Co(+)(HOD), and Co(+)(D(2)O) have been measured from 13,500 to 18,400 cm(-1) using photodissociation spectroscopy. Transitions to four excited electronic states with vibrational and partially resolved rotational structure are observed. Each electronic transition has an extended progression in the metal-ligand stretch, v(3), and the absolute vibrational quantum numbering is assigned by comparing isotopic shifts between Co(+)(H(2)(16)O) and Co(+)(H(2)(18)O). For the low-lying excited electronic states, the first observed transition is to v(3)' = 1. This allows the Co(+)-(H(2)O) binding energy to be determined as D(0)(0 K)(Co(+)-H(2)O) = 13730 ± 90 cm(-1) (164.2 ± 1.1 kJ/mol). The photodissociation spectrum shows a well-resolved K(a) band structure due to rotation about the Co-O axis. This permits determination of the spin rotation constants ε(aa)" = -6 cm(-1) and ε(aa)' = 4 cm(-1). However, the K(a) rotational structure depends on v(3)'. These perturbations in the spectrum make the rotational constants unreliable. From the nuclear spin statistics of the rotational structure, the ground state is assigned as (3)B(1). The electronic transitions observed are from the Co(+)(H(2)O) ground state, which correlates to the cobalt ion's (3)F, 3d(8) ground state, to excited states which correlate to the (3)F, 3d(7)4s and (3)P, 3d(8) excited states of Co(+). These excited states of Co(+) interact less strongly with water than the ground state. As a result, the excited states are less tightly bound and have longer metal-ligand bonds. Calculations at the CCSD(T)/aug-cc-pVTZ level also predict that binding to Co(+) increases the H-O-H angle in water from 104.1° to 106.8°, as the metal removes electron density from the oxygen lone pairs. The O-H stretching frequencies of the ground electronic state of Co(+)(H(2)O) and Co(+)(HOD) have been measured by combining IR excitation with visible photodissociation in a double resonance experiment. In Co(+)(H(2)O) the O-H symmetric stretch is ν(1)" = 3609.7 ± 1 cm(-1). The antisymmetric stretch is ν(5)" = 3679.5 ± 2 cm(-1). These values are 47 and 76 cm(-1), respectively, lower than those in bare H(2)O. In Co(+)(HOD) the O-H stretch is observed at 3650 cm(-1), a red shift of 57 cm(-1) relative to bare HOD.

Previous Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS) experiments have shown that UV/visible photolysis of the fluorene cation leads primarily to sequential loss of one to five hydrogens. Subsequent photolysis of the odd mass dehydrogenated species induces further fragmentation to lower mass products. In the present paper, results from density functional calculations are used to explain the experimental findings. These results show that dehydrogenation is predicted to occur first from the sp 3 carbon on the five-membered ring and then from only one of the six-membered rings. The predicted infrared spectrum of this C 13 H 5 + (m/z 161) species is shown to match well with a matrix isolation spectrum of a photolyzed fluorene sample. The conclusion is drawn that the C 13 H 5 + (m/z 161) ion retains its fluorene-like framework and does not isomerize upon dehydrogenation. Photolysis of this C 13 H 5 + (m/z 161) ion does appear to lead to isomerization. Plausible photodecomposition pathways leading from this (and other) species to the observed low-mass products are shown to be possible only if it is assumed that the fluorene framework opens to a monocyclic ring. Unusual geometries, such as a "tadpole" shape (three-membered ring attached to a linear carbon chain) for the C 5 H 3 + species, a three-membered ring fused to a six-membered ring for the C 7 H 5 + product and monocyclic rings for the all-carbon C 9 + and C 11 + product ions are computed to be the most stable for these observed products.

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We report the results of a time-resolved coincident ion momentum imaging experiment probing nuclear wave packet dynamics in the strong-field ionization and dissociation of iodomethane (CH3I).