Collisional Energy Transfer between Hot Pyrazine and Cold CO:  A Classical Trajectory Study

Abstract

Vibrational energy transfer from hot pyrazine (E′ ) 40 322 cm -1 ) to cold CO is modeled using classical trajectories. Collisional energy transfer properties are studied as a function of the initial rotational state J′ of the CO, the length of the CO, the energy E′ in pyrazine, the relative kinetic energy, the temperature, isotopic substitution on pyrazine, and the intermolecular potential. The energy transfer probability function P(E,E′) exhibits distinct deviation from single exponential behavior. Collisions that transfer particularly large energy are associated with large amplitude out-of-plane motion of a C-H bond, imparting a kick to the departing CO. Slower collisions are particularly effective in relaxing pyrazine; faster collisions can add energy as often as they remove it. Energy transfer properties also depend on the initial rotational state of the CO. Temperature effects on 〈E -E′〉 are weak in the 200-500 K range; this results from an increase in the magnitudes of both 〈∆E〉 down and 〈∆E〉 up . The fraction of pyrazine energy partitioned to translation increases with temperature. Decreasing the rotational temperature of pyrazine (at fixed translational temperature) decreases -〈E -E′〉 significantly. Decreasing translational temperature (at fixed pyrazine rotational temperature) increases -〈E -E′〉. This is in contrast to the conventional expectation, based on Landau-Teller theory. Effects of making modest changes of the intermolecular potential are also discussed. † Part of the special issue "Richard Bersohn Memorial Issue".

Energy transfer between azulene and krypton: Comparison between experiment and computation

“…[44][45][46][47][48][49][50] In addition to the first and second moments of P͑E , EЈ͒ it is possible to obtain mechanistic information on the energy transfer process [48][49][50] and even qualitative information on the shape of P͑E , EЈ͒, including the supercollision tail. Classical trajectory calculations were used to calculate collisional energy transfer quantities mainly in polyatomicmonatomic collisions but also in polyatomic-polyatomic collisions.…”

Energy transfer of highly vibrationally excited molecules studied by crossed molecular beam/time-sliced velocity map ion imaging

“…Chapman and co-workers used quasiclassical trajectory calculations to investigate the energy transfer of highly vibrationally excited pyrazine in collisions with CO at 300 K [116]. They showed that most collisions, typically about 80%, are direct, exhibiting only one turning point in the relative coordinate.…”

“…In the study of energy transfer between pyrazine and CO, Chapman and co-workers also investigated the effects of initial translational energy [116]. They showed that the average energy transfer for energy-up collisions increases as the translational energy increases, but average energy-down collisions does not change.…”

“…They showed, in studies of supercollisions between benzene and Ar, that rotations and out-of-plane motions both play key roles in these collisions [114]. In the study of pyrazine-CO energy transfer [116], Chapman and co-workers showed that the collisions of particularly large energy transfer are associated with large amplitude outof-plane motion of a C-H bond, imparting a kick to the departing CO. Recently, Oref and co-workers reported the classical trajectory calculations of collisional energy transfer between excited azulene and Ar under initial conditions similar to our crossed molecular beam experiments [103].…”

Energy transfer of highly vibrationally excited naphthalene. II. Vibrational energy dependence and isotope and mass effects

“…[14][15][16][17][18][19][20][21][22][23][24][25][26] The calculation indicates how the energy transferred per collision depends on the internal energy of polyatomic molecules, on the intermolecular potential, on the mass of the bath, on the duration of collision, on the minimal distance of approach, on the relative velocity, on the vibrational modes, and on the rotation of polyatomic molecules. [14][15][16][17][18][19][20][21][22][23][24][25][26] The calculation indicates how the energy transferred per collision depends on the internal energy of polyatomic molecules, on the intermolecular potential, on the mass of the bath, on the duration of collision, on the minimal distance of approach, on the relative velocity, on the vibrational modes, and on the rotation of polyatomic molecules.…”