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The collisional energy transfer (CET) in self-collisions of benzene, toluene, p-xylene and azulene is reported. The mechanisms of CET are short, impulsive collisions and long-lived chattering collision where energy is transferred in a sequence of short internal encounters during the lifetime of the collision complex. The dynamical effects are shown to control CET.

The mechanism and quantities of collisional energy transfer, (CET) between an excited benzene and cold benzene and Ar bath are reported. A study is conducted on CET between excited toluene, p-xylene, and azulene with cold benzene and Ar and on CET of excited benzene with cold toluene, p-xylene, and azulene.

Research is done on clusters and collision complexes which are stabilized by three-body collisions that are two-step bimolecular collisions A + B -> AB* and AB* + M -> AB + M, where M is a bath molecule that removes the excess energy from AB. In conclusion, the analytical expressions, which were developed for centrosymmetric potentials, are in poor agreement with the trajectory results of benzene/Ar for low values and in good agreement for high values of translation energies and temperatures.

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]

Collisional energy transfer (CET) and quantities for polyatomic-polyatomic collisions are described and excited benzene collisions with cold benzene bath (B-B) are used as the sample system. The results when compared with the CET of excited benzene with Ar bath showed that the gateway mode for both systems is the out-of-plane modes and that in B-B CET, vibration-vibration, is the dominant channel.

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.