Near shot-noise limited time-resolved circular dichroism pump-probe spectrometer

TL;DR

This paper introduces a highly sensitive, near shot-noise limited time-resolved circular dichroism spectrometer capable of nanosecond resolution, enabling the detection of weak CD signals and transient absorption changes in complex systems.

Contribution

It presents a novel design and data processing protocol for TRCD spectroscopy that achieves near shot-noise limited sensitivity and allows simultaneous measurement of absorption and CD transients.

Findings

Achieved near shot-noise limited sensitivity in TRCD measurements.

First observation of weak TRCD kinetics in the Fenna-Matthews-Olson complex.

Demonstrated simultaneous absorption and CD transient measurements.

Abstract

We describe an optical near shot-noise limited time-resolved circular dichroism (TRCD) pump-probe spectrometer capable of reliably measuring {\mu}deg circular dichroism signal with nanosecond time resolution. Such sensitivity is achieved through a modification of existing TRCD designs and introduction of a new data processing protocol that eliminates approximations that have caused substantial nonlinearities in past measurements and allows the measurement of absorption and CD transients simultaneously with a single pump pulse. The exceptional signal-to-noise ratio of the described setup makes TRCD technique applicable to a large range of non-biological and biological systems. The spectrometer was used to record, for the first time, weak TRCD kinetics associated with triplet state energy transfer in the photosynthetic Fenna-Matthews-Olson antenna pigment-protein complex.