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The experimental and theoretical adiabatic ionization energies (IEs) of the rhodium-holmium bimetallic clusters RhHo2On (n=0–2) have been determined using photoionization efficiency spectroscopy and density functional theory (DFT) calculations. Both sets of data show the IE of RhHo2O to be significantly lower than the values for RhHo2 and RhHo2O2, which are found to be similar. This indicates that there are significant changes in electronic properties upon sequential addition of oxygen atoms to RhHo2. The DFT investigations show that the lowest energy neutral structures are a C2v triangle for RhHo2, a C2v planar structure for RhHo2O where the O atom is doubly bridged to the Ho–Ho bond, and a C2v nonplanar structure for RhHo2O2, where the O2 is dissociative and each O atom is doubly bridged to the Ho–Ho bond in the cluster above and below the RhHo2 trimer plane. Good correlation between the experimental and computational IE data imply that the lowest energy neutral structures calculated are the most likely isomers ionized in the molecular beam. In particular, the theoretical adiabatic IE for the dissociative RhHo2O2 structure is found to compare better with the experimentally determined value than the corresponding lowest energy O2 associative structure. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of the diazomethyl (HCNN) radical have been studied using fast radical beam photofragment translational spectroscopy. A photofragment yield spectrum was obtained for the range of 25 510–40 820 cm-1, and photodissociation was shown to occur for energies above 25 600 cm-1. The only product channel observed was the formation of CH and N2. Fragment translational energy and angular distributions were obtained at several energies in the range covered by the photofragment yield spectrum. The fragment translational energy distributions showed at least two distinct features at energies up to 4.59 eV, and were not well fit by phase space theory at any of the excitation energies studied. A revised C–N bond dissociation energy and heat of formation for HCNN, D0(HC–NN)=1.139±0.019 eV and ΔfH0(HCNN)=5.010±0.023 eV, were determined. [ABSTRACT FROM AUTHOR]

The photodissociation spectroscopy and dynamics resulting from excitation of the B 2A″←X 2A″ transition of CH2CFO have been examined using fast beam photofragment translational spectroscopy. The photofragment yield spectrum reveals vibrationally resolved structure between 29 870 and 38 800 cm-1, extending ∼6000 cm-1 higher in energy than previously reported in a laser-induced fluorescence excitation spectrum. At all photon energies investigated, only the CH2F+CO and HCCO+HF fragment channels are observed. Both product channels yield photofragment translational energy distributions that are characteristic of a decay mechanism with a barrier to dissociation. Using the barrier impulsive model, it is shown that fragmentation to CH2F+CO products occurs on the ground state potential energy surface with the isomerization barrier between CH2CFO and CH2FCO governing the observed translational energy distributions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of I3- from 390 to 290 nm (3.18 to 4.28 eV) have been investigated using fast beam photofragment translational spectroscopy in which the products are detected and analyzed with coincidence imaging. At photon energies ≤3.87 eV, two-body dissociation that generates I-+I2(A 3Π1u) and vibrationally excited I2-(X 2Σu+)+I(2P3/2) is observed, while at energies >=3.87 eV, I*(2P1/2)+I2-(X 2Σu+) is the primary two-body dissociation channel. In addition, three-body dissociation yielding I-+2I(2P3/2) photofragments is seen throughout the energy range probed; this is the dominant channel at all but the lowest photon energy. Analysis of the three-body dissociation events indicates that this channel results primarily from a synchronous concerted decay mechanism. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The photodissociation dynamics of I3- from 390 to 290 nm (3.18 to 4.28 eV) have been investigated using fast beam photofragment translational spectroscopy in which the products are detected and analyzed with coincidence imaging. At photon energies ≤3.87 eV, two-body dissociation that generates I-+I2(A 3Π1u) and vibrationally excited I2-(X 2Σu+)+I(2P3/2) is observed, while at energies >=3.87 eV, I*(2P1/2)+I2-(X 2Σu+) is the primary two-body dissociation channel. In addition, three-body dissociation yielding I-+2I(2P3/2) photofragments is seen throughout the energy range probed; this is the dominant channel at all but the lowest photon energy. Analysis of the three-body dissociation events indicates that this channel results primarily from a synchronous concerted decay mechanism. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]