Abstract

We describe the first implementation of broadband, nanosecond time-resolved step-scan Fourier transform infrared (S²-FT-IR) spectroscopy at a pulse radiolysis facility. This new technique allows the rapid acquisition of nano- to microsecond time-resolved infrared (TRIR) spectra of transient species generated by pulse radiolysis of liquid samples at a pulsed electron accelerator. Wide regions of the mid-infrared can be probed in a single experiment, which often takes < 20–30 min to complete. It is therefore a powerful method for rapidly locating the IR absorptions of short-lived, radiation-induced species in solution, and for directly monitoring their subsequent reactions. Time-resolved step-scan FT-IR detection for pulse radiolysis thus complements our existing narrowband quantum cascade laser-based pulse radiolysis-TRIR detection system, which is more suitable for acquiring single-shot kinetics and narrowband TRIR spectra on small-volume samples and in strongly absorbing solvents, such as water. We have demonstrated the application of time-resolved step-scan FT-IR spectroscopy to pulse radiolysis by probing the metal carbonyl and organic carbonyl vibrations of the one-electron-reduced forms of two Re-based CO₂ reduction catalysts in acetonitrile solution. Transient IR absorption bands with amplitudes on the order of 1 × 10⁻³ are easily detected on the sub-microsecond timescale using electron pulses as short as 250 ns.

© 2022 The Author(s)

Fast time-resolved Fourier-transform spectroscopy for the study of transient chemical reactions

C. A. Carere, W. S. Neil, and J. J. Sloan
Appl. Opt. 35(16) 2857-2866 (1996)

Fast phase-selective detection of transient species with step-scan Fourier-transform spectroscopy

Nathalie Picqué
J. Opt. Soc. Am. B 19(7) 1706-1710 (2002)

Mid-infrared Fourier transform spectroscopy with a broadband frequency comb

Florian Adler, Piotr Masłowski, Aleksandra Foltynowicz, Kevin C. Cossel, Travis C. Briles, Ingmar Hartl, and Jun Ye
Opt. Express 18(21) 21861-21872 (2010)

Infrared intracavity laser absorption spectroscopy with a continuous-scan Fourier-transform interferometer

Jixin Cheng, Hai Lin, Shuiming Hu, Shenggui He, Qingshi Zhu, and Alexander Kachanov
Appl. Opt. 39(13) 2221-2229 (2000)

Step-scan differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS): a spectral deconvolution method for weak absorber detection in the presence of strongly overlapping background absorptions

Lixian Liu, Andreas Mandelis, Huiting Huan, and Kirk H. Michaelian
Opt. Lett. 42(7) 1424-1427 (2017)