The photodissociation of CH3I at 266 nm is investigated by means of high resolution photofragment spectroscopy. The resolution is sufficient to determine the vibrational population of the CH3 umbrella motion for the I*(2P1/2)+CH3 product channel. An approximate vibrational distribution for the I(2P3/2)+CH3 product channel is also determined. The rotational energy distribution for the CH3+I*(2P1/2) channel is estimated to be on the order of or less than 600 cm−1 wide for each of the CH3 vibrational states. A refined value for the C–I bond dissociation energy of 53.3±0.7 kcal/mole is determined from the energy threshold for the I*+CH3 channel. The vibrational energy distribution for the I*+CH3 channel is discussed in relation to a recent model calculation by Shapiro and Bersohn and possible explanations for the discrepency between the calculated and the measured distributions are considered.

The direct absorption spectrum of benzene in a free jet has been measured in the 130-260 nm region (SI , S2' and S3 states, Rydberg series, and the first ionization limit) using synchrotron radiation as a light source. The absolute molar extinction coefficients (E) of benzene in jets have been determined by scaling measured free-jet values to the known value in the vapor phase for a broadband at 200.1 nm in the S2 state. The vibrational temperature for VII> mode was estimated to be 185 K. The maximum value of E of the SI absorption system was found to be 1400 cmol-I em -I (spectral bandwidth = 0.065 nm). A shoulder observed at 205.45 nm in the S2 absorption system is assigned to the S2 origin, induced by pseudo-Jahn-Teller distortion.

The F+D2 and F+HD reactions were investigated in a high resolution crossed molecular beams experiment at several collision energies. The DF product from both reactions was predominantly backward scattered although some forward scattered DF(v=4) was observed at the highest energy studied. The HF angular distributions from F+HD were quite different, showing considerable forward scattered (v=3) and no other identifiable structure. These results disagree with classical trajectory studies, which predict only small variations in the product angular distributions among F+H2 and its isotopic variants. They agree, however, with the predicted dependence of dynamical resonance effects on isotopic substitution. The results therefore support the conclusions drawn in the previous paper regarding the role of dynamical resonances in the F+H2 reaction.

The energy distributions of the primary products of photolysis reactions are of twofold significance. First, the distributions are determined by, and thus are a probe of, the detailed dynamics

The singlet–triplet splitting in methylene has been determined from the measurements of fragment velocities from ketene photodissociation at 351 and 308 nm in a molecular beam. The splitting is found to be 8.5±0.8 kcal/mol. This agrees with many experimental results, but not with the value of 19.5 kcal/mol derived from recent photodetachment experiments on CH−2.

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We have investigated Xe scattering from the graphite(0001) surface at hyperthermal incident energies using a molecular beam-surface scattering technique and molecular dynamics simulations. For all incident conditions, the incident Xe atom conserves the momentum parallel to the surface and loses approximately 80% of the normal incident energy. The weak interlayer potential of graphite disperses the deformation over the wide range of a graphene sheet. The dynamic corrugation induced by the collision is smooth even at hyperthermal incident energy; the graphene sheet moves like a trampoline net and the Xe atom like a trampoliner.

The photoabsorption cross sections and fluorescence excitation spectra of CCl 3 F and CCl 2 F2 were measured using synchrotron radiation at 106-200 nm. The observed absorption bands were accounted for as Rydberg transitions. The emitters produced from the CCl) F and CC1 2 F 2 photodissociative excitations were attributed to CCIF(..4 IA" +-XIA ') and CF 2 (..4 IBI --+X IAI ) transitions, respectively, and their radiative lifetimes were determined to be 626 ± 28 and 58 ± 2 ns. The emission from the CClF(A) starts at 140 nm and increases to 9.1 Mb at 106 nm, and that for CF 2 (A) was deduced to be 0.9 Mb at 104.8 nm. The onsets of the fluorescence suggest that the electronically excited CClF and CF 2 radicals are formed by the atomic Cl elimination but not by molecular C1 2 releasing process.