Measuring absorptive two-dimensional infrared spectra using chirped-pulse upconversion detection

Abstract

Chirped-pulse upconversion (CPU) enables the detection of mid-infrared spectra using a silicon CCD camera by sum-frequency mixing a mid-IR field with a highly chirped near-IR (800 nm) field. Although the substantial chirp limits the spectral broadening and phase distortions caused by the inherent cross-phase modulation, the exquisite phase fidelity needed to measure a fully absorptive two-dimensional IR spectrum demands the correction of the phase distortions. We demonstrate how to correct all of the phase distortions involved in recording an absorptive 2DIR spectrum including delay stage calibrations as well as the requisite nonlinear signals. Besides the extra experimental step of the upconversion process itself, the phase correction procedure requires only the knowledge of the spectral or temporal phase of the chirped pulse. The method is demonstrated in a metal carbonyl complex, Mn2(CO)10, in n-hexane and methanol solvents showing that the method operates well in cases of both homogeneous and inhomogeneous broadening.