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Impact of fullerene ions (C60-) on a metallic surface at keV kinetic energies and under single collision conditions is used as an efficient way for generating gas phase carbide cluster ions of gold and silver, which were rarely explored before. Positively and negatively charged cluster ions, AunCm+ (n = 1-5, 1 ≤ m ≤ 12), AgnCm+ (n = 1-7, 1 ≤ m ≤ 7), AunCm- (n = 1-5, 1 ≤ m ≤ 10), and AgnCm- (n = 1-3, 1 ≤ m ≤ 6), were observed. The Au3C2+ and Ag3C2+ clusters are the most abundant cations in the corresponding mass spectra. Pronounced odd/even intensity alternations were observed for nearly all AunCm+/- and AgnCm+/- series. The time dependence of signal intensity for selected positive ions was measured over a broad range of C60- impact energies and fluxes. A few orders of magnitude immediate signal jump instantaneous with the C60- ion beam opening was observed, followed by a nearly constant plateau. It is concluded that the overall process of the fullerene collision and formation/ejection of the carbidic species can be described as a single impact event where the shattering of the incoming C60- ion into small Cm fragments occurs nearly instantaneously with the (multiple) pickup of metal atoms and resulting emission of the carbide clusters. Density functional theory calculations showed that the most stable configuration of the AunCm+ (n = 1, 2) clusters is a linear carbon chain with one or two terminal gold atoms correspondingly (except for a bent configuration of Au2C+). The calculated AuCm adiabatic ionization energies showed parity alternations in agreement with the measured intensity alternations of the corresponding ions. The Au3C2+ ion possesses a basic Au2C2 acetylide structure with a π-coordinated third gold atom, forming a π-complex structure of the type [Au(π-Au2C2)]+. The calculation shows meaningful contributions of direct gold-gold bonding to the overall stability of the Au3C2+ complex. [ABSTRACT FROM AUTHOR]

Trajectory calculations of collisional energy transfer between excited azulene and Kr are reported, and the results are compared with recent crossed molecular beam experiments by Liu et al. [J. Chem. Phys. 123, 131102 (2005); 124, 054302 (2006)]. Average energy transfer quantities are reported and compared with results obtained before for azulene-Ar collisions. A collisional energy transfer probability density function P(E,E′), calculated at identical initial conditions as experiments, shows a peak at the up-collision branch of P(E,E′) at low initial relative translational energy. This peak is absent at higher relative translational energies. There is a supercollision tail at the down-collision side of the probability distribution. Various intermolecular potentials are used and compared. There is broad agreement between experiment and computation, but there are some differences as well. [ABSTRACT FROM AUTHOR]

Termolecular collisions between a benzene molecule and two Ar atoms were studied by quasiclassical trajectory calculations. The calculations show that termolecular collisions form termolecular complexes and occur by three mechanisms: (a) the Chaperon mechanism, in which the first Ar in is the first Ar out of the termolecular complex, is the dominant one at high pressures. Two-thirds of all termolecular collisions go by this mechanism. (b) The energy transfer mechanism, in which the first Ar in is the last Ar out of the termolecular complex, comprises about a quarter of all termolecular collisions at high pressures. (c) The concerted channel, in which both argon atoms depart from the benzene simultaneously and does not lead to products in reactive systems, comprises about 10% of all termolecular collisions. Energy transfer quantities and collision complex lifetimes in binary and termolecular collisions are evaluated and their dependence on inter- and intramolecular harmonic and anharmonic potentials, temperature, pressure, and internal energy of the benzene molecule are reported. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Average velocities of Ar relative to the center of mass of toluene in bimolecular collisions were determined using quasiclassical trajectory calculations. The collision durations were binned in 20 fs and 100 fs bins and for each bin the velocities of all trajectories were averaged. 10 000 trajectories were calculated. About 64% of all collisions were elastic and the rest were inelastic collisions. The remaining 36% inelastic collisions can be classified into four types. (a) Impulsive collisions of duration 0–300 fs (62%). (b) Chattering collisions of duration longer than 300 fs but shorter than intramolecular vibrational relaxation (IVR) times (>=30%). (c) Complex forming collisions which last longer than molecular IVR times but less than complex (molecular+transition modes) IVR times and complex forming collisions which last longer than complex IVR times. The latter may lead to statistical distribution of energy in the collision complex. These long lived trajectories have negligible contribution to the value of the average energy transferred. (d) Supercollisions (0.12%) which are collisions which transfer an inordinate amount of energy in one event. The details of the collisional process are discussed and sample distributions are presented. Analysis of the collision events indicate that out-of-plane vibrations and overall rotations play a major role in the energy transfer mechanism. A comparison with existing analytical energy transfer models is presented and it is shown that some of them do not agree with the present trajectory calculation results. It is suggested that supercollisions in the gas phase and in solution play a major role in chemical reactions. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Analyzes the quasiclassical trajectory calculations on Li[sup +] ion collision with a C[sub 60] molecule. Account on probabilities of endohedral formation; Dependence of endohedral formation on the relative translational energy; Relationship between endohedral formation and internal energy; Average energy transferred per collision with a fullerene molecule.

Proposes a method to calculate intermolecular energy transfer probability density function from quasi-classical trajectory calculation. Demonstration of the method for benzene-argon collisions; Combination of ab initio inter- and intramolecular potential with trajectory calculation; Global potentials in center-of-mass and minimal distance coordinates.

Studies the collisional energy transfer between argon and normal vibrationally and rotationally frozen internally excited benzene-trajectory calculations. Normal collisional energy transfer; Collisions with initially nonrotating benzene molecules; Comparison of normal collisions and supercollisions.

Computational results on collisional energy transfer between excited and cold azulene and Ar are reported under initial conditions similar to those of crossed molecular beam experiments (Liu, Hsu, Lyu and Ni, J. Chem. Phys. 125 204309 (2006)). The in-plane scattering cross-section is asymmetric with a preference for positive angles. The out-of-plane scattering angle is symmetric in both positive and negative angles with a strong forward scattering peak. In both T → V/R dominates over V → R/T. The double differential cross-section shows a high probability for forward, then sideways and finally, backward scattering. The latter shows relatively high probability for supercollisions. Average energy transfer quantities and collisional energy transfer probability density functions, P(E,E'), are presented and results for Ar and Kr as colliders are compared. At low initial relative translational energies the up-collision branch of P(E,E') shows a peak. This peak, which is absent at higher relative translational energies, is due to the formation of a collision complex. Special attention is paid to the role of rotational energy in the energy transfer process. Changing the rotational temperature from 0.5 K to 2000 K changes the percentage of up and down collisions as well as the values of the average energy transferred quantities. The effect of the translational energy on energy transfer is discussed. There is broad agreement between experiment and computation. [ABSTRACT FROM AUTHOR]

Energy disposal distributions and cluster lifetimes of Ar-benzene clusters (ABC) were studied by quasiclassical trajectory calculations. Four intermolecular potentials, Lennard-Jones, ab initio, and two Buckingham-type potentials, were used in the calculations. The Ar atom was placed in one of the five minima of the potential surface at 0 K. The benzene monomer in ABC at 0 K was excited to various internal energies, and internal energy loss of the monomer following dissociation was calculated. The average energy removed, 〈ΔE〉, depends on the well depth of the potential and on the initial structure of the cluster. The highest value was obtained when the cluster was formed at the deepest well, in which the Ar atom is above the center of the ring. Regardless of the initial structure, it was found that the atom migrated from well to well including the deepest, and dissociation occurred from a structure different from the initial one. No correlation was found between the energy removed and the cluster lifetime, i.e., the dissociation process is history independent. Rotations and out-of-plane vibrations play a major role in the dissociation process. Except for the lowest values of ΔE, the energy disposal probability density function, P(E[sup ′],E), is exponential in ΔE. The cluster lifetime distributions depend on the potential, and can be fit by multiexponential functions. Within a given potential, the shallower the well the narrower the temporal distribution, and the higher the internal energy of ABC the shorter the lifetime. Application of Rice-Ramsperger-Kassel-Marcus (RRKM) theory to cluster modes, which contain an amount of energy ΔE, yields lifetimes with values similar to those obtained directly from trajectory calculations. A comparison is made between P(E[sup ′],E), 〈ΔE〉, and lifetimes obtained in cluster-dissociation and gas-phase collision calculations for identical inter- and intramolecular potentials. Energ... [ABSTRACT FROM AUTHOR]

The possibility of using statistical methods of planning extreme experiments for constructing fusibility diagrams for a triple-component system was demonstrated. The calculated fusibility diagram for the system BaO-ZrO-AlO was constructed in which we distinguished a region for superrefractory compositions. The resulting data should be corrected on the basis of experimental determinations of the refractoriness, since the calculations do not take into account the real reactions in the ternary mixtures. However, the volume of experimentation in this case is sharply reduced. [ABSTRACT FROM AUTHOR]