Rotational Excitation III: Classical Trajectory Methods

Pattengill, M. D.

doi:10.1007/978-1-4613-2913-8_10

Cited by 19 publications

(11 citation statements)

References 31 publications

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“…This is standard procedure used in many studies of molecular collisions. 37 The value of b max corresponds to l max chosen such that no trajectory with angular momenta l > l max can lead to inelastic energy transfer. For the CS calculations, we used the basis set with 16 total angular momenta of the collision complex and the rotational states of the molecule with j = 0-24, which ensures full basis-set convergence.…”

Section: B Comparison Of Classical and Quantum Calculationsmentioning

confidence: 99%

Collision dynamics of polyatomic molecules containing carbon rings at low temperatures

Krems

Heller

2014

The Journal of Chemical Physics

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We explore the collision dynamics of complex hydrocarbon molecules (benzene, coronene, adamantane, and anthracene) containing carbon rings in a cold buffer gas of (3)He. For benzene, we present a comparative analysis of the fully classical and fully quantum calculations of elastic and inelastic scattering cross sections at collision energies between 1 and 10 cm(-1). The quantum calculations are performed using the time-independent coupled channel approach and the coupled-states approximation. We show that the coupled-states approximation is accurate at collision energies between 1 and 20 cm(-1). For the classical dynamics calculations, we develop an approach exploiting the rigidity of the carbon rings and including low-energy vibrational modes without holonomic constraints. Our results illustrate the effect of the molecular shape and the vibrational degrees of freedom on the formation of long-lived resonance states that lead to low-temperature clustering.

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Section: B Comparison Of Classical and Quantum Calculationsmentioning

confidence: 99%

Collision dynamics of polyatomic molecules containing carbon rings at low temperatures

Krems

Heller

2014

The Journal of Chemical Physics

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“…The initial rotational energy of the molecule E rot is determined by diagonalizing the matrix constructed with the hamiltonian for the rotational motion of a free asymmetrictop rigid rotor. We randomly sample the Euler angles and the magnitudes of ω x,y,z with the constraint I x ω 2 x + I y ω 2 y + I z ω 2 z = E rot to ensure that the trajectories cover the entire phase space [34]. The impact parameter b l is chosen quantum mechanically [34]:…”

Section: B Collision Dynamicsmentioning

confidence: 99%

“…We randomly sample the Euler angles and the magnitudes of ω x,y,z with the constraint I x ω 2 x + I y ω 2 y + I z ω 2 z = E rot to ensure that the trajectories cover the entire phase space [34]. The impact parameter b l is chosen quantum mechanically [34]:…”

Section: B Collision Dynamicsmentioning

confidence: 99%

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Cold collisions of complex polyatomic molecules

Heller

2012

The Journal of Chemical Physics

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We introduce a method for classical trajectory calculations to simulate collisions between atoms and large rigid asymmetric-top molecules. We investigate the formation of molecule-helium complexes in buffer-gas cooling experiments at a temperature of 6.5 K for molecules as large as naphthalene. Our calculations show that the mean lifetime of the naphthalene-helium quasi-bound collision complex is not long enough for the formation of stable clusters under the experimental conditions. Our results suggest that it may be possible to improve the efficiency of the production of cold molecules in buffer-gas cooling experiments by increasing the density of helium. In addition, we find that the shape of molecules is important for the collision dynamics when the vibrational motion of molecules is frozen. For some molecules, it is even more crucial than the number of accessible degrees of freedom. This indicates that by selecting molecules with suitable shape for buffer-gas cooling, it may be possible to cool molecules with a very large number of degrees of freedom.

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“…Mean diatomic internuclear separations ⟨ r ⟩ were computed from wave functions derived from the experimental potentials, ,, and the rigid-rotor trajectory calculations used these values. The final rotational actions from simulations were binned to even values of Δ j using the standard histogram method, resulting in level-to-level inelastic cross sections.…”

Section: Methodsmentioning

confidence: 99%

Rotational Energy Transfer in Highly Excited States of Lithium Dimer: Experiment and Modeling

2020

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We report level-resolved rate coefficients for collision-induced rotational energy transfer in the 7Li2 *–Ne system, with 7Li2 * in the highly electronically excited E(3)1Σg +(v i = 4, j i = 31) and F(4)1Σg +(v i = 10, j i = 31) states. The distributions of rate coefficients are strikingly different from those previously measured for the A(1)1Σu +(v i = 2–24, j i = 30) state of the same molecule, falling off much more rapidly with increasing rotational quantum number change |Δj|. The reason for the difference was explored by means of an inverse Monte Carlo approach employing classical trajectories and a model potential, which was adjusted to give agreement with experiment. The modeling strongly suggests that the E and F state interaction potentials are much more nearly isotropic than that of the A state. The resulting dramatic reduction in rate coefficient, especially for large |Δj|, may be relevant in the relaxation of gases at high temperatures.

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Rotational Excitation III: Classical Trajectory Methods

Cited by 19 publications

References 31 publications

Collision dynamics of polyatomic molecules containing carbon rings at low temperatures

Collision dynamics of polyatomic molecules containing carbon rings at low temperatures

Cold collisions of complex polyatomic molecules

Rotational Energy Transfer in Highly Excited States of Lithium Dimer: Experiment and Modeling

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