Isotope effect on the IVR dynamics after ultrafast IR excitation of the hydrogen bond in salicylaldimine

Abstract

The presence of intramolecular hydrogen bonds (HBs) leads to a pronounced anharmonicity of the potential energy surface (PES) for vibrational dynamics. Therefore, HBs can be identified and characterized by the shift and shape of the infrared (IR) absorption of A-H stetching vibrational transitions. The simulation of time-resolved experiments requires the knowledge of the multidimensional PES as well as the solution of the appropriate dynamical equations. Recently, it has been shown that an all-Cartesian reaction surface (CRS) Hamiltonian approach, combined with a high-dimensional nuclear wave packet propagation using the multi-configuration time dependent Hartree (MCTDH) method, provides an ideal setup for studying the intramolecular vibrational energy redistribution (IVR) dynamics of HB systems. Although this emphasizes the intramolecular aspect of the overall dynamics, it may lead to the identification of effective models for the condensed phase case. This chapter extends previous studies on the HB spectroscopy and dynamics of salicylaldimine and focuses on the influence of isotopic H/D substitution on the IVR dynamics. Further, the CRS Hamiltonian is briefly introduced while also discussing numerical results of a seven-dimensional (7D) wave packet propagation.