Simplified and economical 2D IR spectrometer design using a dual acousto-optic modulator

Over the last decade two-dimensional infrared (2D IR) spectroscopy has proven to be a very useful extension of infrared spectroscopy, yet the technique remains restricted to a small group of specialized researchers because of its experimental complexity and high equipment cost. We report on a spectrometer that is compact, mechanically robust, and is much less expensive than previous designs because it uses a single pixel MCT detector rather than an array detector. Moreover, each axis of the spectrum can be collected in either the time or frequency domain via computer programming. We discuss pulse sequences for scanning the probe axis, which were not previously possible. We present spectra on metal carbonyl compounds at 5 μm and a model peptide at 6 μm. Data collection with a single pixel MCT takes longer than using an array detector, but publishable quality data are still achieved with only a few minutes of averaging.

Graphical abstractDownload full-size imageHighlights► We demonstrate the viability of a novel 2D IR spectrometer that uses a dual Ge acousto-optic modulator (AOM). ► The spectrometer uses a single pixel MCT detector rather than an array detector. ► The use of a dual AOM permits ways of scanning 2D IR spectra not previously possible. ► We compare data collection with a single pixel MCT detector to an array detector at 5 and 6 μm. ► We find improved signal-to-noise using a dual AOM because time delays are varied on a shot-to-shot basis.