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Ultrafast non-Adiabatic Processes in Molecules: Recent Advances in Theory and Experiment

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Physical Chemistry and Chemical Physics".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 7259

Special Issue Editors


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Guest Editor
Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
Interests: molecular reaction dynamics; excited state dynamics; probe and exploitation of vibrational and electronic coherences; femtosecond spectroscopy; time-resolved fluorescence for spectroscopy and dynamics

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Guest Editor
Department of Chemistry, Kyungpook National University, Daegu 41566, Korea
Interests: Quantum theory developments for excited state dynamics including recent MRSF-TDDFT as well as REKS. Applications of Non-adiabatic molecular dynamics (NAMD)

Special Issue Information

Dear Colleagues,

The International Journal of Molecular Sciences (ISSN 1422-0067) is currently preparing a Special Issue on the topic "Ultrafast Non-Adiabatic Processes in Molecules: Recent Advances in Theory and Experiment", and we invite you contribute a research article or a review in this Issue, following peer review.

Adiabatic potential energy surfaces (PESs) provided by the Born–Oppenheimer (BO) approximation are central for many chemical processes. For a wide range of excited-state phenomena such as internal conversion, intersystem crossing, energy transfer, charge transfer, and photochemical reactions, however, the BO approximation breaks down because of the couplings between the PESs. When the couplings between electronic states are strong, these non-adiabatic processes occur ultrafast and coherence becomes vital. The field of non-adiabatic processes has recently seen rapid expansion due to the developments in experiment and theory including ultrafast spectroscopies and non-adiabatic molecular dynamics (NAMD). This Special Issue aims to draw researchers in experiment and theory to appreciate the current status in the description of the non-adiabatic processes in electronic excited states, both experimentally and theoretically, and to stimulate the exchange of information between researchers from various disciplines.

Prof. Dr. Taiha Joo
Prof. Dr. Cheol Ho Choi
Guest Editors

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Keywords

  • Ultrafast non-adiabatic processes
  • Non-adiabatic dynamics
  • Ultrafast spectroscopies
  • Non-adiabatic coupling
  • Photoinduced processes

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Published Papers (2 papers)

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Research

23 pages, 2332 KiB  
Article
An Engineered Biliverdin-Compatible Cyanobacteriochrome Enables a Unique Ultrafast Reversible Photoswitching Pathway
by Sean R. Tachibana, Longteng Tang, Liangdong Zhu, Yuka Takeda, Keiji Fushimi, Yoshibumi Ueda, Takahiro Nakajima, Yuto Kuwasaki, Moritoshi Sato, Rei Narikawa and Chong Fang
Int. J. Mol. Sci. 2021, 22(10), 5252; https://doi.org/10.3390/ijms22105252 - 16 May 2021
Cited by 9 | Viewed by 3433
Abstract
Cyanobacteriochromes (CBCRs) are promising optogenetic tools for their diverse absorption properties with a single compact cofactor-binding domain. We previously uncovered the ultrafast reversible photoswitching dynamics of a red/green photoreceptor AnPixJg2, which binds phycocyanobilin (PCB) that is unavailable in mammalian cells. Biliverdin (BV) is [...] Read more.
Cyanobacteriochromes (CBCRs) are promising optogenetic tools for their diverse absorption properties with a single compact cofactor-binding domain. We previously uncovered the ultrafast reversible photoswitching dynamics of a red/green photoreceptor AnPixJg2, which binds phycocyanobilin (PCB) that is unavailable in mammalian cells. Biliverdin (BV) is a mammalian cofactor with a similar structure to PCB but exhibits redder absorption. To improve the AnPixJg2 feasibility in mammalian applications, AnPixJg2_BV4 with only four mutations has been engineered to incorporate BV. Herein, we implemented femtosecond transient absorption (fs-TA) and ground state femtosecond stimulated Raman spectroscopy (GS-FSRS) to uncover transient electronic dynamics on molecular time scales and key structural motions responsible for the photoconversion of AnPixJg2_BV4 with PCB (Bpcb) and BV (Bbv) cofactors in comparison with the parent AnPixJg2 (Apcb). Bpcb adopts the same photoconversion scheme as Apcb, while BV4 mutations create a less bulky environment around the cofactor D ring that promotes a faster twist. The engineered Bbv employs a reversible clockwise/counterclockwise photoswitching that requires a two-step twist on ~5 and 35 picosecond (ps) time scales. The primary forward Pfr → Po transition displays equal amplitude weights between the two processes before reaching a conical intersection. In contrast, the primary reverse Po → Pfr transition shows a 2:1 weight ratio of the ~35 ps over 5 ps component, implying notable changes to the D-ring-twisting pathway. Moreover, we performed pre-resonance GS-FSRS and quantum calculations to identify the Bbv vibrational marker bands at ~659,797, and 1225 cm−1. These modes reveal a stronger H-bonding network around the BV cofactor A ring with BV4 mutations, corroborating the D-ring-dominant reversible photoswitching pathway in the excited state. Implementation of BV4 mutations in other PCB-binding GAF domains like AnPixJg4, AM1_1870g3, and NpF2164g5 could promote similar efficient reversible photoswitching for more directional bioimaging and optogenetic applications, and inspire other bioengineering advances. Full article
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26 pages, 18416 KiB  
Article
Signatures of Conical Intersection Dynamics in the Time-Resolved Photoelectron Spectrum of Furan: Theoretical Modeling with an Ensemble Density Functional Theory Method
by Michael Filatov, Seunghoon Lee, Hiroya Nakata and Cheol-Ho Choi
Int. J. Mol. Sci. 2021, 22(8), 4276; https://doi.org/10.3390/ijms22084276 - 20 Apr 2021
Cited by 9 | Viewed by 2812
Abstract
The non-adiabatic dynamics of furan excited in the ππ* state (S2 in the Franck–Condon geometry) was studied using non-adiabatic molecular dynamics simulations in connection with an ensemble density functional method. The time-resolved photoelectron spectra were theoretically simulated in a wide range [...] Read more.
The non-adiabatic dynamics of furan excited in the ππ* state (S2 in the Franck–Condon geometry) was studied using non-adiabatic molecular dynamics simulations in connection with an ensemble density functional method. The time-resolved photoelectron spectra were theoretically simulated in a wide range of electron binding energies that covered the valence as well as the core electrons. The dynamics of the decay (rise) of the photoelectron signal were compared with the excited-state population dynamics. It was observed that the photoelectron signal decay parameters at certain electron binding energies displayed a good correlation with the events occurring during the excited-state dynamics. Thus, the time profile of the photoelectron intensity of the K-shell electrons of oxygen (decay constant of 34 ± 3 fs) showed a reasonable correlation with the time of passage through conical intersections with the ground state (47 ± 2 fs). The ground-state recovery constant of the photoelectron signal (121 ± 30 fs) was in good agreement with the theoretically obtained excited-state lifetime (93 ± 9 fs), as well as with the experimentally estimated recovery time constant (ca. 110 fs). Hence, it is proposed to complement the traditional TRPES observations with the trXPS (or trNEXAFS) measurements to obtain more reliable estimates of the most mechanistically important events during the excited-state dynamics. Full article
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