Quantum reactive dynamics of elementary chemical processes: time indipendent vs wave-packets methods.

In the last decades, development of new numerical methodologies for calculations of elementary chemical processes coupled with the fast increase of available computational resources, have allowed us to solve numerically quantum mechanical three body problems without introducing any approximation to the dynamics. Generally speaking, two main different approaches have been developed: time independent (most hyperspherical) and wave packets (time dependent) methods. Although the two different approaches should give of course the same results reproducing reactive observables (rate constants, integral and differential cross sections) the mathematical developments in the computational code make advantages and disadvantages of the two methods strongly correlated with the specific reactive phenomena under study so that, in feasible calculations, no all the processes of a system can be studied with both the methods. In the conference, I will show time independent [1-3] and wave packet [4] results for different processes of some prototypical chemical system obtained by me and my research groups, stressing potentiality and limits of the two methodologies used. References: [1] D. De Fazio, S. Cavalli and V. Aquilanti. 'Quantum dynamics and kinetics of the F + H2 and F + D2 reactions at low and ultra-low temperatures. Frontiers in Chemistry, 7 328 (2019). [2] D. De Fazio, S. Cavalli and V. Aquilanti. 'Benchmark Quantum Kinetics at Low Temperatures toward Absolute Zero and Role of Entrance Channel Wells on Tunneling, Virtual States, and Resonances: The F + HD Reaction'. J. Phys. Chem. A, 124 12 (2020). [3] D. De Fazio. 'The H + HeH+ --> He + H2+ reaction from the ultra-cold regime to the three-body breakup: exact quantum mechanical integral cross sections and rate constants'. Phys. Chem. Chem. Phys. 16 11662 (2014). [4] D. De Fazio, A. Aguado and C. Petrongolo. 'Non-adiabatic quantum dynamics of the dissociative charge transfer He+ + H2 --> He + H + H+'. Frontiers in Chemistry 7 249 (2019).