Quantum molecular dynamics of complex systems studied<br/><br/>with MCTDH: Dynamics and IR-spectroscopy of the protonated water<br/><br/>dimer H5O2+ and its isotopologues

Tuesday, January 13, 2009 - 9:10am - 9:40am
EE/CS 3-180
Hans-Dieter Meyer (Ruprecht-Karls-Universität Heidelberg)
In this presentation we discuss a full (15D) quantum simulation of the
infrared absorption spectrum and dynamics of the protonated water dimer
(H5O2+) by the multiconfiguration time-dependent Hartree (MCTDH) method.
The main features of the IR spectrum are explained an assigned, in
particular a complicated doublet structure at about 1000 cm-1 related
to the proton transfer motion, which was not understood. Also the
couplings of various fundamental motions which shape the spectrum
between 800 and 2000 cm-1 are explained and assigned. A picture of the
cation arises in which the central proton motion determines the dynamics
of various other modes, mostly water bending and water pyramidalization.

We show that a full quantum-dynamical description of such a complex
molecular system can be achieved, providing explicative and predictive
power and a very good agreement to available experimental data.
This success is largely due to the use of the MCTDH method, a powerful
algorithm for propagating wavepackets. The basics of the MCTDH algorithm
are briefly discussed.

To account for the interatomic potential and the interaction with the
radiation we make use of the potential energy surface and dipole-moment
surfaces recently developed by Bowman and collaborators, which constitute
the most accurate ab initio surfaces available to date for this system.