Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B03: Spectroscopy in Space and Time I; Frequency Comb Spectroscopy
11:30 AM–2:30 PM,
Monday, March 6, 2023
Room: Room 126
Sponsoring
Unit:
DCP
Chair: Susanna Widicus Weaver, University of Wisconsin-Madison
Abstract: B03.00009 : Capturing tunnelling and wavepacket splitting effects on electronic spectra with Hagedorn wavepackets*
2:18 PM–2:30 PM
Presenter:
Zhan Tong Zhang
(Ecole Polytechnique Federale de Lausanne)
Authors:
Zhan Tong Zhang
(Ecole Polytechnique Federale de Lausanne)
Jiri Vanicek
(Ecole Polytechnique Federale de Lausanne)
In TGA, a single Gaussian wavepacket (GWP) is propagated using classical-like equations under the local harmonic approximation (LHA), which keeps the wavepacket in the Gaussian form. To explore wavepackets that are not well represented by a single GWP, we can use a class of semiclassical wavepackets introduced by Hagedorn (Hagedorn wavepackets, or HWP) that are constructed from a complete orthonormal basis in the form of polynomials times a particular GWP. The time evolution of the GWP parameters associated with such wavepackets retains the simple propagation form as in TGA, while a variational method can be applied to the coefficients of basis functions to account for effects beyond LHA. As a result, the Hagedorn wavepackets can be applied to much higher-dimensional systems than grid-based quantum approaches.
On several examples of double-well and anharmonic potentials, we demonstrate the convergence of the HWP approach to exact quantum results with a sufficient number of basis functions and its ability to treat spectroscopy problems involving quantum tunnelling and wavepacket splitting that commonly arise in chemical dynamics but are beyond the reach of a single thawed GWP.
*This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No. 683069—MOLEQULE) and from the Swiss National Science Foundation within the National Center of Competence in Research "Molecular Ultrafast Science and Technology" (MUST).
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