Experiments explore the influence of different C-H stretching eigenstates of CH3D on the reaction of CH3D with Cl(2P3/2). We prepare the mid |110>|0>(A1,E), mid |200>|>0(E), and mid |100>|0> +nu3 +nu5 eigenstates by direct midinfrared absorption near 6000 cm(-1). The vibrationally excited molecules react with photolytic Cl atoms, and we monitor the vibrational states of the CH2D or CH3 radical products by 2+1 resonance enhanced multiphoton ionization. Initial excitation of the |200>|0>(E) state leads to a twofold increase in CH2D products in the vibrational ground state compared to|100>|0> +nu3 +nu5 excitation, indicating mode-selective chemistry in which the C-H stretch motion couples more effectively to the H-atom abstraction coordinate than bend motion. For two eigenstates that differ only in the symmetry of the vibrational wave function, |110>|0>(A1) and |110>|0>(E), the ratio of reaction cross sections is 1.00 +/- 0.05, showing that there is no difference in enhancement of the H-atom abstraction reaction. Molecules with excited local modes corresponding to one quantum of C-H stretch in each of two distinct oscillators react exclusively to form C-H stretch excited CH2D products. Conversely, eigenstates containing stretch excitation in a single C-H oscillator form predominantly ground vibrational state CH2D products. Analyzing the product state yields for reaction of the |110>|0>(A1) state of CH3D yields an enhancement of 20 +/- 4 over the thermal reaction. A local mode description of the vibrational motion along with a spectator model for the reactivity accounts for all of the observed dynamics.

Vibrational spectra of p-, m-, and o-difluorobenzene cations in the ground electronic states have been measured by vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy. From the MATI spectra, ionization energies of p-, m-, and o-difluorobenzenes to the ionic ground states have been determined to be 73 861±5, 75 332±5, and 75 003±5 cm−1, respectively. A number of vibrational modes, including fundamentals, their combinations, and overtones were distinctly observed in the MATI spectra and could be assigned successfully by comparing with the results from density functional theory calculation at the B3LYP/6-311++G (2df,2pd) level. Appearance of the overtone progression of some totally symmetric vibrations could be explained also in terms of the overlap between the geometrical changes upon ionization and normal mode eigenvectors. Excellent correlation between the experimental and calculated results suggests that p-, m-, and o-difluorobenzene cations in the ground states retain D2h, C2v, and C2v symmetries, respectively, of the corresponding neutrals.

Vibrational spectra in the ground electronic states, X̃ 2B1, of fluoro-, chloro-, bromo-, and iodobenzene cations and in the excited electronic states, B̃ 2B2, of chloro- and bromobenzene cations have been measured by mass-analyzed threshold ionization (MATI) via one-photon excitation with vacuum ultraviolet light. The spectra consist mostly of strong 0–0 bands and fundamentals, overtones, and combinations of totally symmetric a1 modes. In particular, the observed vibrational bands in the B̃ states have been assigned by referring to the assignments for the ionic ground states and those for the neutral molecules. From the MATI spectra, the ionization energies of fluoro-, chloro-, bromo-, and iodobenzene to the ionic ground states have been determined to be 74 229±5, 73 177±5, 72 570±5, and 70 638±5 cm−1, respectively. The ionization energies to the B̃ states have also been determined to be 91 404±5 and 85 822±5 cm−1 for chloro- and bromobenzene, respectively.

Methyl vinyl ketone (MVK), a volatile compound with photochemical activity, has received considerable attention in the fields of environmental chemistry and atmospheric chemistry. We explored the conformational stabilities of MVK...

One-photon MATI spectra of phenylacetylene and benzonitrile were obtained by using vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. Accurate ionization energies of phenylacetylene and benzonitrile were determined from the positions of the 0−0 bands, which are 8.8195 ± 0.0006 and 9.7288 ± 0.0006 eV, respectively. Vibrational frequencies of the molecular ions were determined from the spectra also. Assignments were made by utilizing the symmetry selection rule and frequencies and Franck−Condon factors calculated at the BP86, B3LYP, and B3PW91 density functional theory levels with the 6-311++G(2df,2pd) basis set.