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Transient Electronic Absorption Spectroscopy


Figure 1. TVAS experimental setup.

Transient Electronic Absorption Spectroscopy is the time resolved study of the absorption spectrum of a sample as a function of time, following excitation from a femtosecond laser pulse. The excitation pulse can be tuned to any wavelength in the range ~235-1600 nm using an optical parametric amplifier (TOPAS), seeded with a 1 kHz, 40 fs, 800 nm pulse (Ti:Sapphire Spitfire ACE) to create pulse powers of around 10 uJ / pulse. The probe pulse is a white light continuum, created by focussing the fundemental 800 nm laser onto a CaF2 window, producing light of ~330-730 nm. The excitation pulse pases through the sample, refreshed for each pulse pair by use of either a flow cell or gravity jet apparatus, to prepare the sample in some electronically excited state. The white light probe then passes through the excited sample after some delay time, which can be varied by way of a gold retroreflector mounted on a delay stage which increases the path length of the 800 nm beam creating the probe pulse. The white light is mointored with a spectrometer (Avantes), which also takes dark backgrounds and unpumped spectra to find the difference in absorption following excitation. By taking a number of these difference asborption spectra over time, a picture of the dynamics of the excited state can be revealed.

The stage that generates the delay between pump and probe pulses has a travel range of 500 mm with a resolution of 5 microns, reproducible to within 0.5 microns. This corresponds to a maximum temporal window of 3.3 nanoseconds at a resolution of 17 femtoseconds. The Avantes spectrometer has a resultion of 1.2 nm, with an intergration time of 0.85 miliseconds, allowing a maximum sample rate of 1.1 kHz, thus fully sampling the 1 kHz laser. It has a 900 nm spectral range, though typically only ~400 nm is utilised in the TEAS experiment. It can store up to 1254 spectra to RAM at any given time.

Recent publications including TEAS results
image The role of symmetric functionalisation on photoisomerisation of a UV commercial chemical filter

J.M. Woolley, J.S. Peters, M.A.P. Turner, G.J. Clarkson, M.D. Horbury and V.G. Stavros
Phys. Chem. Chem. Phys. (2019) [ref]

image Determination of secondary species in solution through pump-selective transient absorption spectroscopy and explicit-solvent TDDFT

M.A.P. Turner, M.D. Horbury, V.G. Stavros and N.D.M. Hine
J. Phys. Chem. A, 123 (2019) 873

image Substituent position effects on sunscreen photodynamics: a closer look at methyl anthranilate

N. D. N. Rodrigues, N. Cole-Filipiak, M. A. P. Turner, K. Krokidi, G. L. Thornton, G. W. Richings, N. D. M. Hines and V. G. Stavros.
Chem. Phys. 515, 596-602 (2018) [ref]

image Unravelling the Photoprotection Properties of Mycosporine Amino Acid Motifs

Jack M. Woolley, Michael Staniforth, Michael D. Horbury, Gareth W. Richings, Martin Wills, and Vasilios G. Stavros
J. Phys. Chem. Lett. 9:3043 (May 2018) [ ref ]

image Ultrafast transient absorption spectroscopy of the sunscreen constituent ethylhexyl triazone

L.A. Baker, S. Clark, S. Habershon and V.G. Stavros
J. Phys. Chem. Lett. 8 2113-2118 (2017) [ref]

image Photophysics of the sunscreen ingredient menthyl anthranilate and its precursor methyl anthranilate: a bottom-up approach to photoprotection

N. D. N. Rodrigues, N. Cole-Filipiak, M. D. Horbury, M. Staniforth, T. N. V. Karsili, Y. Peperstraete and V. G. Stavros J. Photochem. Photobio. A. 353, 376-384 (2018) [ref]

image Investigating isomer specific photoprotection in a model plant sunscreen

M. D. Horbury, A.L. Flourat, S.E. Greenough, F. Allais and V.G. Stavros.Chem. Commun., 54, 936-939 (2018) [ref]

image First Step toward a Universal Fluorescent Probe: Unravelling the Photodynamics of an Amino–Maleimide Fluorophore

Michael Staniforth, Wen-Dong Quan, Tolga N. V. Karsili, Lewis A. Baker, Rachel K. O’Reilly, and Vasilios G. Stavros
J. Phys. Chem. A, 121:6357 (August 2017)

WCUS and affiliates publish a brand new work in which we discuss fluorescence quenching in a small, single moleucle fluorophore, and how learning the mechanism of this quenching can aid us in future design of new fluorescent tags.

image Elucidating nuclear motions in a plant sunscreen during photoisomerization through solvent viscosity effects

M. D. Horbury, W.-D. Quan, A. L. Flourat, F. Allais and V. G. Stavros. Phys. Chem. Chem. Phys. (2017) 19, 21127-21131 [ref]

image Photoisomerization of ethyl ferulate: A solution phase transient absorption study

M. D. Horbury, L. A. Baker, N. D. N. Rodrigues, W. -D. Quan and V. G. Stavros Chem. Phys. Lett. 673, 62-67 (2017) [ref]