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Ultrafast broadband circular dichroism in the deep ultraviolet

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Oppermann Malte, Bauer Benjamin, Rossi Thomas, Zinna Francesco, Helbing Jan, Lacour Jérôme, Chergui Majed,
Project Probing local peptide structure and dynamics with UV labels and non-linear spectroscopy
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Original article (peer-reviewed)

Journal Optica
Volume (Issue) 6(1)
Page(s) 56 - 56
Title of proceedings Optica
DOI 10.1364/optica.6.000056

Open Access

URL https://www.osapublishing.org/optica/abstract.cfm?uri=optica-6-1-56
Type of Open Access Publisher (Gold Open Access)

Abstract

The measurement of chirality and its temporal evolution are crucial for the understanding of a large range of biological functions and chemical reactions. Steady-state circular dichroism (CD) is a standard analytical tool for measuring chirality in chemistry and biology. Nevertheless, its push into the ultrafast time domain and in the deep-ultraviolet has remained a challenge, with only some isolated reports of subnanosecond CD. Here, we present a broadband time-resolved CD spectrometer in the deep ultraviolet (UV) spectral range with femtosecond time resolution. The setup employs a photoelastic modulator to achieve shot-to-shot polarization switching of a 20 kHz pulse train of broadband femtosecond deep-UV pulses (250–370 nm). The resulting sequence of alternating left- and right-circularly polarized probe pulses is employed in a pump-probe scheme with shot-to-shot dispersive detection and thus allows for the acquisition of broadband CD spectra of ground- and excited-state species. Through polarization scrambling of the probe pulses prior to detection, artifact-free static and transient CD spectra of enantiopure [Ru(bpy)_3]^2+ are are successfully recorded with a sensitivity of <2 × 10^−5 OD (≈0.7 mdeg). Due to its broadband deep-UV detection with unprecedented sensitivity, the measurement of ultrafast chirality changes in biological systems with amino-acid residues and peptides and of DNA oligomers is now feasible.
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