Symmetry controlled excited state dynamics

2019 ◽  
Vol 21 (5) ◽  
pp. 2283-2294 ◽  
Author(s):  
Max D. J. Waters ◽  
Anders B. Skov ◽  
Martin A. B. Larsen ◽  
Christian M. Clausen ◽  
Peter M. Weber ◽  
...  
Keyword(s):  
Excited State ◽  
Internal Conversion ◽  
Rydberg States ◽  
Aliphatic Amines ◽  
Velocity Map Imaging ◽  
Excited State Dynamics ◽  
Loss Of Coherence

Symmetry effects in internal conversion are studied by means of two isomeric cyclic tertiary aliphatic amines in a velocity map imaging (VMI) experiment on the femtosecond timescale. We conclude that lessening the symmetry of the molecule leads to loss of coherence after internal conversion between Rydberg states.

Picosecond excited-state dynamics in octahedral cobalt(III) complexes: intersystem crossing versus internal conversion

1993 ◽  
Vol 32 (4) ◽  
pp. 394-399 ◽  
Author(s):  
James K. McCusker ◽  
Kevin N. Walda ◽  
Douglas Magde ◽  
David N. Hendrickson
Keyword(s):  
Excited State ◽  
Internal Conversion ◽  
Intersystem Crossing ◽  
Excited State Dynamics

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 Ultrafast valence to non-valence excited state dynamics in a common anionic chromophore

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
James N. Bull ◽  
Cate S. Anstöter ◽  
Jan R. R. Verlet
Keyword(s):  
Excited State ◽  
Internal Conversion ◽  
Rydberg States ◽  
Bound State ◽  
Photoactive Yellow Protein ◽  
Coumaric Acid ◽  
Photoelectron Imaging ◽  
Time Resolved ◽  
Valence States

AbstractNon-valence states in neutral molecules (Rydberg states) have well-established roles and importance in photochemistry, however, considerably less is known about the role of non-valence states in photo-induced processes in anions. Here, femtosecond time-resolved photoelectron imaging is used to show that photoexcitation of the S1(ππ*) state of the methyl ester of deprotonated para-coumaric acid – a model chromophore for photoactive yellow protein (PYP) – leads to a bifurcation of the excited state wavepacket. One part remains on the S1(ππ*) state forming a twisted intermediate, whilst a second part leads to the formation of a non-valence (dipole-bound) state. Both populations eventually decay independently by vibrational autodetachment. Valence-to-non-valence internal conversion has hitherto not been observed in the intramolecular photophysics of an isolated anion, raising questions into how common such processes might be, given that many anionic chromophores have bright valence states near the detachment threshold.

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

2021 ◽  
Author(s):  
Sarah E. Krul ◽  
Sean J. Hoehn ◽  
Karl Feierabend ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Ground State ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Water Mixture ◽  
Relaxation Dynamics ◽  
Similar Time ◽  
Excited State Dynamics ◽  
Computational Calculations

<p>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 and in a mixture of methanol and water using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient spectra are collected using photon densities that ensure no parasitic multiphoton-induced signal from solvated electrons. The data can be fit satisfactorily using a two- or three-component kinetic model. By analyzing the results from steady-state, time-resolved, computational calculations, and the methanol-water mixture, the following general relaxation mechanism is proposed for both molecules, L<sub>b</sub> ® L<sub>a</sub> ® <sup>1</sup>ps*(ICT) ® S<sub>0</sub>, where the <sup>1</sup>ps*(ICT) stands for an intramolecular charge transfer excited singlet state with significant ps* character. In general, longer lifetimes for internal conversion are obtained for 7-deazaguanosine compared to guanosine 5’-monophosphate. Internal conversion of the <sup>1</sup>ps*(ICT) state to the ground state occurs on a similar time scale of a few picoseconds in both molecules. 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 alter the topology of their potential energy surfaces in such a way that the relaxation dynamics in 7-deazaguanosine are slowed down compared to those in guanosine 5’-monophosphate but not for the internal conversion of <sup>1</sup>ps*(ICT) state to the ground state.</p>

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

2021 ◽  
Author(s):  
Sarah E. Krul ◽  
Sean J. Hoehn ◽  
Karl Feierabend ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Ground State ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Water Mixture ◽  
Relaxation Dynamics ◽  
Similar Time ◽  
Excited State Dynamics ◽  
Computational Calculations

<p>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 and in a mixture of methanol and water using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient spectra are collected using photon densities that ensure no parasitic multiphoton-induced signal from solvated electrons. The data can be fit satisfactorily using a two- or three-component kinetic model. By analyzing the results from steady-state, time-resolved, computational calculations, and the methanol-water mixture, the following general relaxation mechanism is proposed for both molecules, L<sub>b</sub> ® L<sub>a</sub> ® <sup>1</sup>ps*(ICT) ® S<sub>0</sub>, where the <sup>1</sup>ps*(ICT) stands for an intramolecular charge transfer excited singlet state with significant ps* character. In general, longer lifetimes for internal conversion are obtained for 7-deazaguanosine compared to guanosine 5’-monophosphate. Internal conversion of the <sup>1</sup>ps*(ICT) state to the ground state occurs on a similar time scale of a few picoseconds in both molecules. 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 alter the topology of their potential energy surfaces in such a way that the relaxation dynamics in 7-deazaguanosine are slowed down compared to those in guanosine 5’-monophosphate but not for the internal conversion of <sup>1</sup>ps*(ICT) state to the ground state.</p>

Excited-state dynamics and viscosity-dependent internal conversion in 3,3-dimethyl-2-phenyl-3H-indole

1993 ◽  
Vol 201 (1-4) ◽  
pp. 145-152 ◽  
Author(s):  
Michel Belletête ◽  
Ranjit S. Sarpal ◽  
Gilles Durocher
Keyword(s):  
Excited State ◽  
Internal Conversion ◽  
Excited State Dynamics
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