Hideki Katayanagi

NONADIABATIC BENDING DISSOCIATION IN 16 VALENCE ELECTRON SYSTEM OCS

The speed, angular, and alignment distributions of S(1D2) atoms from the ultraviolet photodissociation of OCS have been measured by a photofragment imaging technique. From the excitation wavelength dependence of the scattering distribution of S(1D2), the excited states accessed by photoabsorption were assigned to the A′ Renner–Teller component of the u20091Δ and the A″(1Σ−) states. It was found that the dissociation from the A′ state gives rise to high- and low-speed fragments, while the A″ state only provides the high-speed fragment. In order to elucidate the dissociation dynamics, in particular the bimodal speed distribution of S atoms, two-dimensional potential energy surfaces of OCS were calculated for the C–S stretch and bending coordinates by ab initio molecular orbital (MO) configuration interaction (CI) method. Conical intersections of 1Δ and 1Σ− with 1Π were found as adiabatic dissociation pathways. Wave packet calculations on these adiabatic surfaces, however, did not reproduce the low-speed compone...

C–Br bond rupture in 193 nm photodissociation of vinyl bromide

Abstract Photofragment ion imaging has been applied to 193 nm photodissociation of vinyl bromide to measure the speed and angular distributions of Br atoms. Br atoms were observed in both spin–orbit states ( 2 P J ; J =1/2 or 3/2) with the branching ratio, [Br*]/[Br], of 0.06±0.03. Both Br( 2 P J ) distributions were dominated by anisotropic high translational energy components, which are ascribed to C–Br bond rupture via surface crossing between the optically-excited 1 (π,xa0π*) state and 1 (n(Br) or π(Br), σ*(C–Br)) repulsive state(s). The anisotropy parameters of the high translational energy components, 1.3 (Br) and 1.2 (Br*), provide the direction of the transition dipole moment for the π*xa0←xa0π transition to be 26±3° from the Cue605C bond axis, in good agreement with ab initio calculations by Yamashita. Despite that the available energy is 10.5 kcal mol −1 smaller in the Br* channel, the peak energies of P ( E T ) in the Br* and Br channels were quite similar, indicating that the fine structure branching occurs in the molecular region. The low translational energy components of Br and Br* observed are ascribed to the dissociation of VBr from the ground state, although contribution from the secondary dissociation of C 2 H 2 Br radical is also suggested for the Br channel. The anisotropy of the low energy component implies that the lifetime of the ground state VBr is shorter than its rotational period (4.7 μs).

Communication: Mass-analyzed velocity map imaging of thermal photofragments from C60

The velocity distributions of the fragments produced by dissociative photoionization of C(60) have been measured in the extreme UV region for the first time, by using a flight-time resolved velocity map imaging technique combined with a high-temperature molecular beam and synchrotron radiation. Values of the average kinetic energy release were estimated at six different photon energies with respect to five reaction steps of sequential C(2) ejection, starting from C(60)(2+)-->C(58)(2+)+C(2) to C(52)(2+)-->C(50)(2+)+C(2). The translational temperatures of the fragment ions were found to be lower than those obtained by laser multiphoton absorption of C(60). The kinetic energies released in the first to fourth steps increase with increasing hnu and reach 0.35-0.5 eV at hnu=102 eV, reflecting statistical redistribution of the excess energy in the transition state, whereas that in the fifth step leading to C(50)(2+) was exceptionally small.

Mass-analyzed velocity map imaging of doubly charged photofragments from C70

The velocity distributions of the fragments produced by dissociative photoionization of C(70) have been measured at several photon energies in the extreme UV region, by using a flight-time resolved velocity map imaging (VMI) technique combined with a high-temperature molecular beam and synchrotron radiation. Average kinetic energy release was estimated for the six reaction steps of consecutive C(2) emission, starting from C(70)(2+) → C(68)(2+) + C(2) to C(60)(2+)→ C(58)(2+) + C(2). The total kinetic energy generated in each step shows a general tendency to increase with increasing hν, except for the first and fifth steps. This propensity reflects statistical redistributions of the excess energy in the transition states for the above fragmentation mechanism. Analysis based on the finite-heat-bath theory predicts the detectable minimum cluster sizes at the end of the C(2)-emission decay chain. They accord well with the minimum sizes of the observed ions, if the excess energy in the primary C(70)(2+) is assumed to be smaller by ~15 eV than the maximum available energy. The present VMI experiments reveal remarkably small kinetic energy release in the fifth step, in contradiction to theoretical predictions, which suggests involvement of other fragmentation mechanisms in the formation of C(60)(2+).

Photoabsorption cross section of C70 thin films from visible to vacuum ultraviolet

Absolute photoabsorption cross sections of C(70) thin films were determined for hv values from 1.3 to 42 eV using photon attenuation. The spectrum showed a prominent peak of 1320 Mb at 21.4 eV with several fine structures mostly due to sigma-->sigma(*) single-electron excitation. The complex refractive index and complex dielectric function were calculated up to 42 eV with Kramers-Kronig analyses. From the present data of C(70) thin films, the cross section curve of molecular C(70) was calculated using the standard Clausius-Mossotti relation dealing with correction of the local electromagnetic field, with a plausible assumption that the anisotropy in molecular structure of C(70) was smeared out by molecular rotation at room temperature.

Photofragment Imaging Apparatus for Measuring Momentum Distributions in Dissociative Photoionization of Fullerenes

Description is made on a design of a new version of photofragment imaging spectrometer which will be applied to observe the momentum distributions of ionic fragments from large molecules, clusters, and fullerenes. The apparatus consists of several components: a three‐element velocity focusing lens system, a time‐of‐flight drift tube, a potential‐switcheable mass gate, an ion reflector, and a position sensitive detector. The velocity focusing lens system of Eppink‐Parker type [Eppink and Parker, Rev. Sci. Instrum. 68, 3477 (1997)] realizes high‐resolution photofragment images. Moreover, the mass gate is incorporated inside the tube in order to separate fragment ions with a particular cluster size (e.g. C58+) from those with other sizes (e.g. C60+ and C56+). The optimum arrangement and dimensions of the components are determined from the results of ion trajectories of C56+, C58+, and C60+ simulated by using the SIMON software. The calculated images of C58+ ions show that kinetic‐energy resolution of 10 meV ...

Fragmentation Mechanism of Highly Excited C70 Cations in the Extreme Ultraviolet

The ion yield curves for C70−2nz+ (n = 1–8, z = 2 and 3) produced by photoionization of C70 were measured in the photon energy (hv) range of 25 – 150 eV. The appearance hv values were higher by ca. 34 eV than the thermochemical thresholds for dissociative ionization of C70 leading to C70−2nz+. Evaluation was made on the upper limits of the internal energies of the primary C70z+ above which C70−2n+2z+ fragments cannot escape from further dissociating into C70−2nz++C2. These critical internal energies agreed well with appearance internal energies of C70z+ theoretically obtained corresponding to the threshold for the formation of C70−2nz+. The photofragmentation of the parent C70z+ ions is considered to be governed by the mechanism of internal conversion of their electronically excited states, statistical redistribution of the excess energy among a number of vibrational modes, and sequential ejection of the C2 units.An interesting protocol for classical teleportation of an unknown classical state was recently suggested by Cohen, and by Gour and Meyer. In that protocol, Bob can sample from a probability distribution P that is given to Alice, even if Alice has absolutely no knowledge about P . Pursuing a similar line of thought, we suggest here a limited form of nonlocality — “classical nonlocality”. Our nonlocality is the (somewhat limited) classical analogue of the Hughston-Jozsa-Wootters (HJW) quantum nonlocality. The HJW nonlocality (also known as “quantum remote steering”) tells us how, for a given density matrix ρ, Alice can generate any ρ-ensemble on the North Star. This is done using surprisingly few resources — one shared entangled state (prepared in advance), one generalized quantum measurement, and no communication. Similarly, our classical non locality (which we call “classical remote steering”) presents how, for a given probability distribution P , Alice can generate any P-ensemble on the North Star, using only one correlated state (prepared in advance), one (generalized) classical measurement, and no communication. It is important to clarify that while the classical teleportation and the classical non-locality protocols are probably rather insignificant from a classical information processing point of view, they significantly contribute to our understanding of what exactly is quantum in their well established and highly famous quantum analogues.