Energy Transfer In Polyatomic Molecules Research Articles

Collisional energy transfer in polyatomic molecules at high temperatures: Master equation analysis of vibrational relaxation of shock-heated alkanes

Collisional energy transfer plays an important role in unimolecular reaction kinetics. This Letter presents classical trajectory calculations of the energy transfer processes in collisions between selected alkanes (ethane, propane, isobutane, and neopentane) and krypton at high temperature. The primary aim of this study was to elucidate the validity of the predicted energy transfer parameters by performing master equation analyses of their vibrational relaxation times and comparing the predicted values with the available experimental data. The results demonstrate the ability of classical trajectory calculations to accurately predict the parameters for vibrational energy transfer.

超快强激光场中多原子分子电离及能量转移过程

超快强激光场中多原子分子电离及能量转移过程

Collisional energy transfer in polyatomic molecules in the gas phase

AbstractThis paper is an attempt to present an overall view of energy transfer between excited polyatomic molecules and polyatomic and monatomic bath, based on results obtained by classical trajectory calculations. It is not a general review of the subject but a summary based on work done by us in the last few years. We report average energies transferred in a collision and collisional energy transfer probability density functions for various collision partners as a function of various system parameters: temperature, vibrational and rotational energies of the hot and cold molecule, and relative translational energies. Various mechanisms for energy transfer are proposed, their dependence on the system parameters is explored, and the relevance of empirical numerical models to computational results is discussed.

Semiclassical model for energy transfer in polyatomic molecules. XIV. He- and Ar-glyoxal collisions

Cross sections and rate constants for vibrational excitation of the ν 7 mode in glyoxal by collisions with He and Ar atoms are calculated by a quantum-classical model. Comparison with approximate quantum calculations and experimental data is made.

Mode mixing and chaos induced by potential surface crossings

The effect of Born–Oppenheimer potential energy surface crossings on energy transfer in polyatomic molecules is investigated, classically and quantum mechanically. The hopping from one energy surface to another is enough to cause classical chaos, and strong mixing of the levels quantum mechanically. The rate of classical mixing determines the extent of quantum mixing, even though classical mixing is complete at long times.

Semiclassical model for energy transfer in polyatomic molecules. XIII. Biomolecules

We have formulated a semiclassical approach to energy transfer in large polyatomic molecules in which the rigid part of the molecule is treated quantum mechanically within a harmonic operator formalism whereas motions like the CH 3 torsional motion and translation of the incoming atom/molecule are treated classically. As an example we consider energy transfer for an α-helix of alanine by collisions with He atoms.

Semiclassical calculation of energy transfer in polyatomic molecules. XII. Organic molecules

A semiclassical method for energy transfer to the torsional motion of polyatomic molecules is presented. It is shown that a purely classical treatment of the torsional motion is problematic due to the zero-point vibrational energy which may migrate into other modes. State-to-state cross sections for the excitation of the CH 3 torsion in CH 3OH colliding with 4He are presented as a function of initial kinetic energy.

Semiclassical calculation of energy transfer in polyatomic molecules. XI. Cross sections and rate constants for Ar + CO2

Abstract Data from electron gas calculation on the short-range potential and theoretical van der Waals coefficients C n ( n = 6, 8) have been used to construct a potential surface for the Ar+CO 2 system. The surface has been used to calculate: second virial coefficient, viscosity and diffusion coefficient, rotational relaxation rates, rate constants for vibrational transitions in CO 2 and high-enery/small-angle differential cross sections.

Dynamics of vibrational energy transfer in polyatomic molecules. A model calculation

Abstract The master equation for polyatomic molecules in diluted polyatomic bath gas is solved for a vibrational energy transfer probability model. The temporal evolution of a population at a given equilibrium temperature or excited to a single energy level is reported as a function of the size, the temperature and criteria for equilibrium. It is found that the smaller the size of the molecules and the lower the temperature, the less collisions are needed to obtain equilibrium. It is also found that the number of collisions needed to obtain equilibrium is insensitive to the initial level within a certain range and sensitive outside it and that it depends on the criteria for equilibrium. In both single energy level and initial distribution, the final Boltzmann distribution is not preceded by a succession of Boltzmann distributions.

Semiclassical calculation of energy transfer in polyatomic molecules. IX. Cross sections for M + CO 2 (000) → M + CO 2( nml) (M = He and Ar)

Cross sections for excitation of the asymmetric-stretch vibrational manifold of CO 2 in collision with He and Ar have been calculated using a semiclassical collision method and a potential-energy surface constructed from self-consistent field data. The cross sections for collisional energies up to 2.0 eV are compared with those obtained in a molecular-beam experiment.

Semiclassical calculation of energy transfer in polyatomic molecules. X. Energy transfer in Ar + SF6 at 1 eV

Abstract Rotational and vibrational energy transfer in Ar + SF 6 collisions at 1 eV is calculated as a function of scattering angle. Differential cross sections for the two most excited vibrational modes ν 6 and ν 5 are also reported.

Semiclassical calculation of energy transfer in polyatomic molecules. VIII. Theory for atom + non-linear triatom

The theory for collision of an atom with a non-linear triatomic molecule is presented and the He + H2O system considered as an example. It is shown that both anharmonic and Coriolis coupling are important for the energy transfer. Seventeen rate constants for vibrational transitions in H2O are calculated in the temperature range 300–2000 K.

On a semiclassical approach to energy transfer by atom/molecule-surface collisions

A semiclassical theory for energy transfer in polyatomic molecules has been extended to atom/molecule-surface scattering problems. The solid is treated

Semiclassical calculation of rate costants for energy transfer between the asymmetric stretch mode of CO 2 and N 2

By using a semiclassical method for energy transfer in polyatomic molecules we have calculated 21 rate constants for vibration-vibration transitions between the asymmetric stretch mode of CO 2 and the vibrational mode of N 2 in the temperature range 50–700 K.

Semiclassical calculation of energy transfer in polyatomic molecules. VII. Intra- and inter-molecular energy transfer in N 2 + CO 2

Rate constants for inter- and intra-molecular energy transfer in the N 2 + CO 2 system are obtained in the temperature range 200–2000 K with three different sets of potential short-range parameters. Comparison with available experimental data is carried out. The analytical solution to the “inversion problem” for the M-quantum case is also presented.

Semiclassical calculation of energy transfer in polyatomic molecules. VI. On the theory for linear triatomic molecules

The degeneracy of the bending mode of linear triatomic molecules has been included in a semiclassical theory for energy transfer in polyatomic molecules. By introducing suitable transformations it is possible to reduce the coupling scheme to an M = 2 quantum problem for the vibrational angular momentum transitions and an M = 3 quantum problem for the coupling between the three normal modes. Comparison is made with previous calculations on Ne + CO 2 where the degeneracy was neglected.

Semiclassical calculation of energy transfer in polyatomic molecules. V. Differential cross sections for excitation of CO 2 and N 2O colliding with Li + at E ≈ 4.72 eV

A semiclassical model has been used to calculate differential cross sections for vibrational excitation of CO 2 and N 2O at the center of mass collision energy E≈ 4.72 eV. Also the average rotational excitation as a function of the scattering angle is reported. Comparison is made with experimental data and previous more approximate theoretical calculations.

Semiclassical calculation of energy transfer in polyatomic molecules. IV. A graphic method for solution of the M-quantum case

The vibrational energy transfer in a polyatomic molecule is described by introducing an irreducible set of operators. Each operator represents a specific interaction induced by the intermolecular potential. We present a graphic method which significantly facilitates the solution if the number of quantum modes ( M) is large.

Semiclassical calculation of energy transfer in polyatomic molecules. III. Rate constants for energy transfer in Ne + CO 2

A semiclassical method has been used to calculate rate constants for energy transfer in CO 2 colliding with Ne. The Coriolis and anharmonic coupling terms are included in the model. The sensitivity of the results to changes in the intermolecular potential is investigated. The deactivation at the 001 state of CO 2 is found to be due to the 001 → 110 transition. This transition is induced by the cubic term of the intermolecular potential in a normal mode expansion.

Comparison of harmonic and anharmonic matrix elements: application to vibrational energy transfer

Vibrational matrix elements for harmonic as well as different anharmonic wavefunctions are compared using an exponential form for the dependence on the internal coordinate. The general formulas are given and applied to SO 2, H 2O and CH 4. The application to vibrational energy transfer in polyatomic molecules is discussed in detail.