scholarly journals Femtosecond Transient Absorption Studies of Simple Polyenes in Solution

1999 ◽  
Vol 19 (1-4) ◽  
pp. 371-374
Author(s):  
Kaoru Ohta ◽  
Yukito Naitoh ◽  
Keisuke Tominaga ◽  
Noboru Hirota ◽  
Keitaro Yoshihara
Keyword(s):  
Ground State ◽  
Vibrational Relaxation ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Visible Region ◽  
Single Bond ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies ◽  
Bond Proceeds ◽  
Subnanosecond Time

We have conducted femtosecond transient absorption experiments on the excited-state dynamics of trans- and cis-hexatriene (HT) in solution. The transient absorption in the visible region decays with the time constant of about 500 fs, indicating that the internal conversion (IC) to the ground state occurs quite efficiently. The bleach recovery signal contains several time constants. The vibrational relaxation in the ground state occurs in 10–20ps and the slow relaxation process, which may be due to the conformational change around C—C single bond, proceeds in a subnanosecond time scale.

scholarly journals Femtosecond Transient Absorption Studies of Two Novel Energetic Tetrazole Derivatives

2021 ◽  
pp. 100016
Author(s):  
Naga Krishnakanth Katturi ◽  
Chinmoy Biswas ◽  
Nagarjuna Kommu ◽  
Sai Santosh Kumar Raavi ◽  
Venugopal Rao Soma
Keyword(s):  
Transient Absorption ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies ◽  
Tetrazole Derivatives

Covalent decoration onto the outer walls of double walled carbon nanotubes with perylenediimides

2015 ◽  
Vol 3 (19) ◽  
pp. 4960-4969 ◽  
Author(s):  
Myriam Barrejón ◽  
Sara Pla ◽  
Isadora Berlanga ◽  
María J. Gómez-Escalonilla ◽  
Luis Martín-Gomis ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Charge Separation ◽  
Transient Absorption ◽  
Femtosecond Transient Absorption ◽  
Covalently Bonded ◽  
Absorption Studies ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Three new covalently bonded DWCNT–PDIs have been synthesized and characterized, showing exclusively functionalization of the outer walls leaving the inner walls intact. Femtosecond transient absorption studies were performed to seek evidence of charge separation in these hybrids.

Femtosecond Transient Absorption Studies of Energy Transfer within Chromophore-Labeled Dendrimers

2001 ◽  
Vol 105 (7) ◽  
pp. 1307-1312 ◽  
Author(s):  
Frederik V. R. Neuwahl ◽  
Roberto Righini ◽  
Alex Adronov ◽  
Patrick R. L. Malenfant ◽  
Jean M. J. Fréchet
Keyword(s):  
Energy Transfer ◽  
Transient Absorption ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies

Femtosecond transient absorption studies of electrons in liquid alkanes

1995 ◽  
Vol 99 (19) ◽  
pp. 7436-7438 ◽  
Author(s):  
Frederick H. Long ◽  
Hong Lu ◽  
Kenneth B. Eisenthal
Keyword(s):  
Transient Absorption ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies ◽  
Liquid Alkanes

Excited state electron transfer in A2 and A2B2 functionalized zinc porphyrins carrying rigid and flexible β-pyrrole π-extended substituents

2020 ◽  
Vol 24 (05n07) ◽  
pp. 904-919
Author(s):  
Michael B. Thomas ◽  
Siddhartha Kumar ◽  
Timothy Esquivel ◽  
Hong Wang ◽  
Francis D’Souza
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Transient Absorption ◽  
Binding Constants ◽  
Free Energy Calculations ◽  
Stable Complex ◽  
State Electron ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies ◽  
Zinc Porphyrins

Optical absorption and emission, electrochemical, and photochemical properties of peripherally functionalized with flexible and rigid [Formula: see text]-extended substituents on A2 and A2B2 type zinc porphyrins is investigated. The significance of rigid [Formula: see text]-substituents over flexible ones in governing the spectral properties is unraveled. Flexible [Formula: see text]-substituents on the porphyrin ring caused appreciable spectral broadening compared to porphyrin carrying rigid [Formula: see text]-substituents. Further, supramolecular dyads are formed by coordinating phenyl imidazole functionalized fullerene, C[Formula: see text]Im. The calculated binding constants for the 1:1 complexes is in the order of 2–7 × 105 M[Formula: see text] suggesting stable complex formation. Free-energy calculations performed according to the Rehm–Weller approach suggested possibility of excited state electron transfer in these dyads. Femtosecond transient absorption studies of the dyads performed in [Formula: see text]-dichlorobenzene showed evidence of occurrence of electron transfer from the singlet-excited state that was in competition with the intersystem crossing process to populate the triplet-excited state of porphyrins.

scholarly journals Ultralong UV/mechano-excited room temperature phosphorescence from purely organic cluster excitons

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xuepeng Zhang ◽  
Lili Du ◽  
Weijun Zhao ◽  
Zheng Zhao ◽  
Yu Xiong ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Efficiency ◽  
Transient Absorption ◽  
Transient State ◽  
Exciton Model ◽  
Room Temperature Phosphorescence ◽  
Naphthalic Anhydride ◽  
Femtosecond Transient Absorption ◽  
Organic Solid ◽  
Absorption Studies

AbstractPurely organic room temperature phosphorescence (RTP) has attracted wide attention recently due to its various application potentials. However, ultralong RTP (URTP) with high efficiency is still rarely achieved. Herein, by dissolving 1,8-naphthalic anhydride in certain organic solid hosts, URTP with a lifetime of over 600 ms and overall quantum yield of over 20% is realized. Meanwhile, the URTP can also be achieved by mechanical excitation when the host is mechanoluminescent. Femtosecond transient absorption studies reveal that intersystem crossing of the host is accelerated substantially in the presence of a trace amount of 1,8-naphthalic anhydride. Accordingly, we propose that a cluster exciton spanning the host and guest forms as a transient state before the guest acts as an energy trap for the RTP state. The cluster exciton model proposed here is expected to help expand the varieties of purely organic URTP materials based on an advanced understanding of guest/host combinations.

The geometry relaxation and photodeactivation from the S2 state of dibenzofuran studied by ultrafast spectroscopy

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1495-1506 ◽  
Author(s):  
Lian Wang ◽  
Song Zhang ◽  
Ye Wang ◽  
Bing Zhang
Keyword(s):  
Excited State ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Excited State Absorption ◽  
Transient Absorption Spectroscopy ◽  
Femtosecond Transient Absorption ◽  
Pharmaceutically Active Compound ◽  
S2 State ◽  
Franck Condon ◽  
T State

AbstractDibenzofuran (DBF) has attracted much attention from scientists recently since it is applied as a photoluminescence material and pharmaceutically active compound. Since the polychlorinated derivatives are highly toxic and manifest photostability in the environment. Femtosecond transient absorption spectroscopy associated with quantum chemical calculations are employed to investigate the ultrafast excited state dynamics of dibenzofuran from the S2 state in 1,4-dioxane and ethanol, respectively. Following excitation at a wavelength of 266 nm, the S2 state is firstly populated in the Franck–Condon region and preserves the planar molecular structure of the ground state. The observed increase of the transient absorption spectra of the excited state within the first several picoseconds indicates a geometry relaxation occurring on the S2 potential energy surface. The subsequent kinetic traces of excited state absorption show that the S2 state in the adiabatic region decays to the S1 state through a fast internal conversion, followed by intersystem crossing to the T1 state with a decay time of tens and hundreds of picoseconds in ethanol and 1,4-dioxane, respectively. Finally, the deactivation processes from the S1 or T state are slow and take place on a time scale of about 20 ns.

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>

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