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DY: Fachverband Dynamik und Statistische Physik

DY 41: Statistical Physics: General

DY 41.2: Talk

Thursday, March 21, 2024, 09:45–10:00, BH-N 128

Perturbative approach to non-linear non-Markovian vibrational spectroscopy — •Hélène Colinet — AG Netz, FU Berlin

Using perturbation theory, we investigate how non-harmonic potential contributions and non-Markovian friction influence vibrational absorption spectra, in particular the OH stretch band in liquid water. Non-Markovian friction gives rise to homogeneous and inhomogeneous line broadening of vibrational bands and is accurately accounted for using the generalized Langevin equation.

Our analytical results are validated by numerical simulations of the generalized Langevin equation, by which we demonstrate that our perturbation theory successfully reproduces changes in line shape and position. In particular, we show that the non-harmonic bond potential is crucial for resolving the inhomogeneous line broadening of the OH stretch band in the infrared absorption spectrum of liquid water. For this, anharmonic bond potentials and time-dependent friction kernels are extracted from ab initio molecular dynamics simulations.

Keywords: General Langevin equation; spectroscopy