Collisional Intermolecular Energy Transfer from a N2 Bath at Room Temperature to a Vibrationlly "Cold" C6F6 Molecule
Amit K Paul1,2, Diego Donzis3, William L Hase1
1Department of Chemistry and Biochemistry, Texas Tech University , Lubbock, Texas 79409, United States.
The Journal of Physical Chemistry. A
|May 10, 2017
Summary
Collisional energy transfer from nitrogen (N₂) to cold hexafluorobenzene (C₆F₆) was simulated. Energy transfer rates depend on energy difference, not temperature ratio, and C₆F₆ energy distribution broadens during transfer.
Area of Science:
- Chemical Dynamics
- Molecular Collisions
- Energy Transfer
Background:
- Understanding intermolecular energy transfer is crucial for chemical kinetics and thermodynamics.
- Previous studies investigated energy transfer from N₂ to hot C₆F₆, providing a baseline for comparison.
- The vibrational temperature of C₆F₆ was set to 50 K and 0 K, significantly colder than the N₂ bath (300 K).
Purpose of the Study:
- To investigate collisional intermolecular energy transfer from a thermalized N₂ bath to vibrationally cold C₆F₆.
- To determine the influence of temperature ratio on energy transfer dynamics.
- To analyze the specific modes involved in energy transfer and their impact on C₆F₆ energy distribution.
Main Methods:
- Chemical dynamics simulations were employed to model the energy transfer process.
- Simulations tracked the average energy of C₆F₆ over time, fitting the data to a biexponential function.
- The study compared energy transfer rates and mechanisms for cold C₆F₆ with previous simulations of hot C₆F₆.
Main Results:
- The average energy of C₆F₆ versus time was accurately described by a biexponential function.
- Energy transfer rates (k₁ and k₂) differed significantly from those of hot C₆F₆, with a faster initial rate and a slower long-term rate.
- The average energy transferred per collision was dependent on the energy difference between C₆F₆ and the bath, but independent of the C₆F₆/N₂ temperature ratio.
- Translational and rotational energy from N₂ transferred to C₆F₆ vibrations, while N₂ vibrational energy and C₆F₆ translational/rotational energies remained constant.
- The energy distribution of C₆F₆ broadened as it gained energy from the N₂ bath.
Conclusions:
- Collisional energy transfer dynamics are sensitive to the initial vibrational state of the acceptor molecule.
- The observed broadening of the C₆F₆ energy distribution indicates a complex energy flow within the molecule during thermalization.
- The findings provide detailed insights into the fundamental processes governing intermolecular energy transfer in gas-phase collisions.
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