Scattering Elimination of Heterodyne-Detected Two-Dimensional Infrared Spectra Using Choppers and Shutters

Obtaining high-quality 2D IR spectra of heterogeneous samples such as perovskite films or metal–organic framework powder is hampered by severe light scattering. In the pump–probe (PP) method, this problem can be circumvented by phase cycling. However, in the heterodyned photon echo (HPE) method, phase cycling does not function as effectively as the PP method. This study demonstrates that the scattering problem can be solved mechanically by introducing another chopper and two shutters into the existing 2D IR setup without moving any translation stages to introduce a phase shift in the HPE method. For a perovskite film having a very rough surface, containing a small amount of residual dimethylformamide, and having a maximum absorbance of ∼0.0004 in the CO stretch region, this advanced experimental method is tested and proven to be highly effective.