The intense Σu+1←X1Σg+ electronic transition of the chains HC2nH (n=8–13) has been recorded in the gas phase using resonant two color two photon ionization spectroscopy. The gas phase frequencies lie ∼1300 cm−1 to the blue of the values in a neon matrix. These polyynes appear to be linear in both the ground and the excited state and, as for the polyynes, spectral and theoretical evidence for large bond alternation in the ground state is found indicating localized π orbitals on the C≡C units. These species are the longest carbon chains observed spectroscopically in the gas phase up to now.

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The electronic spectra of the C 2n H͑D͒ Ϫ , nϭ2 -4, anions have been observed in the gas phase using photodetachment spectroscopy. These are assigned to 1 ⌸←X 1 ⌺ ϩ electronic transitions. The 1 ⌸ excited states possess a dipole bound character indicated by the energetic proximity between the origin of the transitions and electron affinities. The dipole bound states are related to the X 2 ⌸ ground states of C 6 H and C 8 H whereas for C 4 H, which has an X 2 ⌺ ϩ ground state, the 2 ⌸ is an excited state. Vibronic coupling through a bending motion of the carbon skeleton is inferred to be the reason of the stabilization of this state.

Chemiluminescence experiments have been performed to assess the state of current CO * 2 kinetics modeling. The difficulty with modeling CO * 2 lies in its broad emission spectrum, making it a challenge to isolate it from background emission of species such as CH * and CH 2 O * . Experiments were performed in a mixture of 0.0005H 2 + 0.01N 2 O + 0.03CO + 0.9595Ar in an attempt to isolate CO * 2 emission. Temperatures ranged from 1654 K to 2221 K at two average pressures, 1.4 and 10.4 atm. The unique time histories of the various chemiluminescence species in the unconventional mixture employed at these conditions allow for easy identification of the CO * 2 concentration. Two different wavelengths to capture CO * 2 were used; one optical filter was centered at 415 nm and the other at 458 nm. The use of these two different wavelengths was done to verify that broadband CO * 2 was in fact being captured, and not emission from other species such as CH * and CH 2 O * . As a baseline for time history and peak magnitude comparison, OH * emission was captured at 307 nm simultaneously with the two CO * 2 filters. The results from the two CO * 2 filters were consistent with each other, implying that indeed the same species (i.e., CO * 2 ) was being measured at both wavelengths. A first-generation kinetics model for CO * 2 and CH 2 O * was developed, since no comprehensively validated one exists to date. CH 2 O * and CH * were ruled out as being present in the experiments at any measurable level, based on calculations and comparisons with the data. Agreement with

The unimolecular reactions of the fluoromethane ion have been investigated by the threshold photoelectron photoion coincidence technique (TPEPICO). The breakdown curves have been measured in the energy range between the adiabatic ionization potential of 12.53 eV and 21 eV. In this energy range the formation of the CH 2 F + , CHF + , CH 2 + , CH 3 + , and CF + fragment ions is observed. The appearance energies (AE) for these ions at 300 K are 13.2, 13.91, 13.93, 14.51 and < 17.7 eV respectively. The 0 K threshold energy for the formation of CH 2 F + ions is 13.37 eV. Two different pathways for the unimolecular reaction of the fluoromethane ion can be distinguished. The reaction proceeding through the electronic ground state of the ion is entirely statistical. In contrast to this the reaction occurring through the first electronic excited state shows nonstatistical behaviour. The two pathways are distinguished via the kinetic energy released in the respective dissociation channels. While all thermochemically allowed reaction channels are observed on the ion ground state potential, the first excited state seems to decay predominantly by F loss reaction.