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QUANTUM DYNAMICS OF FINITE ATOMIC AND MOLECULAR SYSTEMS THROUGH DENSITY MATRIX METHODS

Brian Thorndyke

Published Jan 1, 2004• 2 citations
OpenAlex

Abstract

) vs. time, for the Li-surface system. . 554{11 Expectation of position and dispersion for the Na-surface system. . . 564{12 Expectation of momentum and dispersion for the Na-surface system. 574{13 Density function ˆ(R) for the Na-surface system. . . . . . . . . . . . 584{14 Potential curves for the dual avoided crossing collision. . . . . . . . . 614{15 Populations 

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) vs. time, for the Li-surface system. . 554{11 Expectation of position and dispersion for the Na-surface system. . . 564{12 Expectation of momentum and dispersion for the Na-surface system. 574{13 Density function ˆ(R) for the Na-surface system. . . . . . . . . . . . 584{14 Potential curves for the dual avoided crossing collision. . . . . . . . . 614{15 Populations 
The ultracold reaction offers a unique opportunity to elucidate the intricate microscopic mechanism of chemical reactions, and the Na 2 Li system serves as a pivotal reaction system in the investigation of ultracold reactions. In this work, a high-precision potential energy surface (PES) of the Na 2 Li system is constructed based on high-level ab initio energy points and the neural network (NN) method, and a proper asymptotic functional form is adopted for the long-range interaction, which is suitable for the study of cold or ultracold collisions. Based on the new NN PES, the dynamics of the Li + Na 2 ( v = 0, j = 0) → Na + NaLi reaction are studied in the collision energy range of 10 –7 to 80 cm –1 . In the high collision energy range of 8 to 80 cm –1, the dynamics of the reaction is studied using the time-dependent wave packet method and the statistical quantum mechanical (SQM) method. Comparing the results of the two methods, it is found that the SQM method provides a rough description of the product ro-vibrational state distribution but overestimates the integral cross-section values. With the decrease of collision energy, the reaction differential cross section gradually changes from forward–backward symmetric scattering to predominant forward scattering. In the low collision energy range from 10 –7 to 8 cm –1, the SQM method is used to study the reaction dynamics, and the rate constant in the Wigner threshold region is estimated to be 2.87 × 10 –10 cm 3 /s.
We present triplet and singlet scattering lengths for X--133Cs collisions (X=6,7Li, 23Na, 39,40,41K, and 85,87Rb). We consider the short-range potential-energy curves based on high-quality ab initio calculations and the long-range potential described by accurate dispersion coefficients available in the literature. Using a Fermi function to smoothly connect the short- and long-range terms we construct the potential for all R and evaluate the scattering length for each mixed species X--Cs. In particular, we predict that the cross section for inelastic processes between 23Na and 133Cs and between 40K and 133Cs will be small as compared with the respective elastic cross sections.