Quantum dynamics of ultracold Na+ Na2 collisions

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Chemical Dynamics

Background:

• Ultracold collisions are fundamental to understanding quantum phenomena in atomic and molecular systems.
• Investigating spin-polarized sodium (Na) atoms and vibrationally excited sodium dimer (Na2) molecules provides insights into reactive scattering processes.

Purpose of the Study:

• To theoretically investigate ultracold collisions between spin-polarized Na atoms and vibrationally excited Na2 molecules.
• To analyze the influence of different potential energy surfaces (pairwise additive and nonadditive) on collision outcomes.
• To determine the dominant processes (vibrational relaxation vs. elastic scattering) at extremely low temperatures.

Main Methods:

• Utilizing a reactive scattering formalism that incorporates atom exchange.
• Performing calculations on both pairwise additive and nonadditive potential energy surfaces for the quartet electronic state.
• Applying Wigner threshold laws for energies below 10^-5 K.

Main Results:

• Vibrational relaxation processes were found to dominate over elastic processes at temperatures below 10^-3–10^-4 K.
• Rate coefficients for vibrational relaxation (v=1 to 0) at temperatures below 10^-5 K were calculated as 4.8x10^-11 cm^3 s^-1 (additive) and 5.2x10^-10 cm^3 s^-1 (nonadditive).
• A significant difference in rate coefficients highlights the sensitivity to the chosen potential energy surface.

Conclusions:

• Ultracold collisions involving sodium atoms and molecules are strongly influenced by vibrational relaxation at low temperatures.
• The choice of potential energy surface significantly impacts the calculated rate coefficients, underscoring the need for accurate surface representations.
• Theoretical modeling of these systems is essential for predicting and understanding quantum effects in ultracold chemistry.