Temperature dependence of the hydrated electron’s excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

2017 ◽  
Vol 147 (7) ◽  
pp. 074504 ◽  
Author(s):  
Erik P. Farr ◽  
Chen-Chen Zho ◽  
Jagannadha R. Challa ◽  
Benjamin J. Schwartz
Keyword(s):  
Excited State ◽  
Temperature Dependence ◽  
Emission Spectroscopy ◽  
Transient Absorption ◽  
Relaxation Mechanism ◽  
Stimulated Emission ◽  
Ultrafast Transient Absorption

Observation of stimulated emission and ultrafast transient absorption dynamics from a novel alkyl-substituted PPV

1997 ◽  
Vol 84 (1-3) ◽  
pp. 663-664
Author(s):  
Benjamin J. Schwartz ◽  
Fumitomo Hide ◽  
Mats R. Andersson ◽  
Alan J. Heeger
Keyword(s):  
Transient Absorption ◽  
Stimulated Emission ◽  
Ultrafast Transient Absorption

Ultrafast excited state dynamics of S2 and S1 states of triphenylmethane dyes

2014 ◽  
Vol 16 (31) ◽  
pp. 16824-16831 ◽  
Author(s):  
Pallavi Singhal ◽  
Hirendra N. Ghosh
Keyword(s):  
Excited State ◽  
Transient Absorption ◽  
Tricarboxylic Acid ◽  
Triphenylmethane Dyes ◽  
Excited State Dynamics ◽  
Bromopyrogallol Red ◽  
Pyrogallol Red ◽  
Ultrafast Transient Absorption

Excited state dynamics of S2 and S1 states for a series of TPM dyes, pyrogallol red (PGR), bromopyrogallol red (Br-PGR) and aurin tricarboxylic acid (ATC), have been monitored by using ultrafast transient absorption and fluorescence up-conversion techniques.

scholarly journals Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate in Aqueous Solution

2020 ◽  
Author(s):  
Sarah E. Krul ◽  
Sean J. Hoehn ◽  
Karl Feierabend ◽  
Carlos Crespo-Hernández
Keyword(s):  
Aqueous Solution ◽  
Excited State ◽  
Potential Energy Surfaces ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Relaxation Mechanism ◽  
Transient Absorption Spectroscopy ◽  
Experimental Conditions ◽  
Excited State Dynamics ◽  
Computational Calculations

Minor structural modifications to the DNA and RNA nucleobases have a significant effect on their excited state dynamics and electronic relaxation pathways.<b> </b>In this study, the excited state dynamics of 7-deazaguanosine and guanosine 5’-monophosphate are investigated in aqueous solution using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient absorption spectra are collected under experimental conditions that eliminate the requirement to correct the data for the formation of hydrated electrons, resulting from the two-photon ionization of the solvent. The data is fitted satisfactorily using a two-component sequential kinetic model, yielding lifetimes of 210 ± 50 fs and 1.80 ± 0.02 ps, and 682 ± 40 fs and 1.4 ± 0.03 ps, for 7-deazaguanosine and guanosine 5’-monophosphate, respectively. By analyzing the results from steady-state, time-resolved, and computational calculations, the following relaxation mechanism is proposed for 7-deazaguanosine, S<sub>2</sub>(L<sub>b</sub>) ® S<sub>1</sub>(L<sub>a</sub>) ® S<sub>0</sub>, whereas a S<sub>2</sub>(L<sub>b</sub>) ® S<sub>1</sub>(L<sub>a</sub>) ® S<sub>0</sub>(hot)<sub> </sub>® S<sub>0 </sub>relaxation mechanism<sub> </sub>is proposed for guanosine 5’-monophosphate. Interestingly, longer lifetimes for both the L<sub>b</sub> ® L<sub>a</sub> and the L<sub>a</sub> ® S<sub>0</sub> internal conversion pathways are obtained for 7-deazaguanosine compare to guanosine 5’-monophosphate. Collectively, the results demonstrate that substitution of a single nitrogen for a methine (C-H) group at position seven of the guanine moiety stabilizes the <sup>1</sup>pp* L<sub>b</sub> and L<sub>a</sub> states and alters the topology of their potential energy surfaces in such a way that the population dynamics of both internal conversion pathways in 7-deazaguanosine are significantly slowed down compared to those in guanosine 5’-monophosphate.

scholarly journals Femtosecond visible transient absorption spectroscopy of chlorophyll-f-containing photosystem II

2020 ◽  
Vol 117 (37) ◽  
pp. 23158-23164
Author(s):  
Noura Zamzam ◽  
Rafal Rakowski ◽  
Marius Kaucikas ◽  
Gabriel Dorlhiac ◽  
Sefania Viola ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Photosystem Ii ◽  
Charge Separation ◽  
Transient Absorption ◽  
Spectral Feature ◽  
Cation Radical ◽  
Stimulated Emission ◽  
Transient Absorption Spectroscopy ◽  
Long Wavelength

The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a. We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d. The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1+•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210–1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.

Ultrafast transient absorption microscopy: Study of excited state dynamics in PtOEP crystals

2016 ◽  
Vol 464 ◽  
pp. 69-77 ◽  
Author(s):  
Dar’ya Davydova ◽  
Alejandro de la Cadena ◽  
Stefan Demmler ◽  
Jan Rothhardt ◽  
Jens Limpert ◽  
...  
Keyword(s):  
Excited State ◽  
Transient Absorption ◽  
Microscopy Study ◽  
Excited State Dynamics ◽  
Ultrafast Transient Absorption

scholarly journals Spatial confinement alters the ultrafast photoisomerization dynamics of azobenzenes

2020 ◽  
Vol 11 (35) ◽  
pp. 9513-9523
Author(s):  
Christopher J. Otolski ◽  
A. Mohan Raj ◽  
Vaidhyanathan Ramamurthy ◽  
Christopher G. Elles
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Water Soluble ◽  
Transient Absorption Spectroscopy ◽  
Guest Complex ◽  
Spatial Confinement ◽  
Excited State Dynamics ◽  
Host Guest Complex ◽  
Ultrafast Transient Absorption

Ultrafast transient absorption spectroscopy reveals new excited-state dynamics following excitation of trans-azobenzene (t-Az) and several alkyl-substituted t-Az derivatives encapsulated in a water-soluble supramolecular host–guest complex.

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