Nanosecond Time-Resolved Infrared Spectroscopy with a Dispersive Scanning Spectrometer

TLDR

Time‑resolved infrared spectroscopy is positioned as a promising technique relative to infrared laser spectroscopy and Fourier transform infrared spectroscopy. The system employs a high‑temperature ceramic infrared source, a photovoltaic MCT detector, and a custom low‑noise, wide‑band preamplifier. A nanosecond‑resolution infrared spectrometer was built, achieving 50‑ns time resolution and 10⁻⁶ sensitivity, and demonstrated on photochemical and photobiological samples while revealing that thermal artifacts arise from transient reflectance changes due to small temperature jumps.

Abstract

A nanosecond time-resolved infrared spectroscopic system based on a dispersive scanning spectrometer has been constructed. This is an advanced version of a similar system reported in a previous paper; the time resolution has been improved from 1 μs to 50 ns and the sensitivity from 10 −4 in intensity changes to 10 −6 . These have been achieved by the use of a high-temperature ceramic infrared light source, a photovoltaic MCT detector, and a low-noise, wide-band preamplifier developed specifically for the present purpose. Time-resolved infrared spectra of a few samples of photochemical and photobiological interests are presented to show the capability of the system. The origin of the thermal artifacts, which have been found to hamper the time-resolved infrared measurements seriously, is shown to be due to the transient reflectance change induced by a small temperature jump. The future prospect of time-resolved infrared spectroscopy is discussed with reference to other methods including infrared laser spectroscopy and Fourier transform infrared spectroscopy.