Application of 2D IR to investigate the structure and dynamics of highly scattering-producing samples

Abstract

Acquiring high-quality 2D IR spectra for heterogeneous samples is limited by severe scattering from the samples. This talk presents a mech. approach to overcome the scattering problem by introducing two addnl. choppers into a conventional photon echo-type 2D IR apparatus Besides, studies on the structure and dynamics of highly scattering-producing samples are presented, including perovskite films, an NO-containing organometallic compound in the form of powders and KBr pellets, islet amyloid polypeptide (IAPP) oligomers, and DO dissolved in CHCl. With the perovskite films, two peaks that cannot be easily identified with the conventional FTIR spectroscopy were observed in the C=O stretch region. A vibrational ladder-climbing process up to v = 5 is observed for the NO-containing organometallic compound For IAPP oligomers, 2D IR spectra of various IAAP mutants in the early aggregation stages show that aggregation pathways are markedly different between the mutants. For the case of monomeric DO in CHCl, the coupling between the sym. and antisym. O-D stretch is systematically investigated using polarization-dependent 2D IR spectroscopy with numerical 2D simulations based on the exciton-band theory. The accurate parameters related to the coupling are obtained, and the relaxation in the harmonic approximation is also quantified.