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Title: Nonadiabatic nuclear dynamics of the ammonia cation studied by surface hopping classical trajectory calculations

The Landau–Zener (LZ) type classical-trajectory surface-hopping algorithm is applied to the nonadiabatic nuclear dynamics of the ammonia cation after photoionization of the ground-state neutral molecule to the excited states of the cation. The algorithm employs a recently proposed formula for nonadiabatic LZ transition probabilities derived from the adiabatic potential energy surfaces. The evolution of the populations of the ground state and the two lowest excited adiabatic states is calculated up to 200 fs. The results agree well with quantum simulations available for the first 100 fs based on the same potential energy surfaces. Three different time scales are detected for the nuclear dynamics: Ultrafast Jahn–Teller dynamics between the excited states on a 5 fs time scale; fast transitions between the excited state and the ground state within a time scale of 20 fs; and relatively slow partial conversion of a first-excited-state population to the ground state within a time scale of 100 fs. Beyond 100 fs, the adiabatic electronic populations are nearly constant due to a dynamic equilibrium between the three states. The ultrafast nonradiative decay of the excited-state populations provides a qualitative explanation of the experimental evidence that the ammonia cation is nonfluorescent.
Authors:
 [1] ;  [2] ; ;  [3]
  1. Department of Theoretical Physics, Herzen University, St. Petersburg 191186 (Russian Federation)
  2. Department Chemie, Technische Universität München, D-85747 Garching (Germany)
  3. Zentrum Mathematik, Technische Universität München, D-85747 Garching (Germany)
Publication Date:
OSTI Identifier:
22415505
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ALGORITHMS; AMMONIA; CATIONS; COMPUTERIZED SIMULATION; EQUILIBRIUM; EXCITED STATES; GROUND STATES; JAHN-TELLER EFFECT; LANDAU-ZENER FORMULA; MOLECULES; PHOTOIONIZATION; POTENTIAL ENERGY; PROBABILITY; QUANTUM MECHANICS; SURFACES; TRAJECTORIES