Benchmark of Excitation Energy Shifts from Frozen-Density Embedding Theory: Introduction of a Density-Overlap-Based Applicability Threshold

2018 ◽  
Vol 14 (8) ◽  
pp. 4028-4040 ◽  
Author(s):  
Alexander Zech ◽  
Niccolò Ricardi ◽  
Stefan Prager ◽  
Andreas Dreuw ◽  
Tomasz A. Wesolowski
Keyword(s):  
Excitation Energy ◽  
Embedding Theory

Thymine Dimerization Induced by Oxidative DNA Lesions and Epigenetic Intermediates via Triplet-Triplet Energy Transfer

2020 ◽  
Author(s):  
Mauricio Lineros-Rosa ◽  
Antonio Francés-Monerris ◽  
Antonio Monari ◽  
Miguel Angél Miranda ◽  
Virginie Lhiaubet-Vallet
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Dna Lesions ◽  
Transient Absorption Spectroscopy ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Dna Nucleobases

Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidative lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer the excitation energy to thymine-thymine dyads, inducing the formation of the highly toxic and mutagenic cyclobutane pyrimidine dimers (CPDs). By using steady-state and transient absorption spectroscopy, NMR, HPLC, and theoretical calculations, we quantify the differences in the triplet-triplet energy transfer mediated by ForU and ForC, revealing that the former is much more efficient in delivering the excitation energy and producing the CPD photoproduct. Although significantly slower than ForU, ForC is also able to harm DNA nucleobases and therefore this process has to be taken into account as a viable photosensitization mechanism. The present findings evidence a rich photochemistry crucial to understand DNA photodamage and of potential use in the development of biomarkers and non-conventional photodynamic therapy agents.

Benchmark of the Extension of Frozen-Density Embedding Theory to Nonvariational Correlated Methods: The Embedded-MP2 Case

2021 ◽  
Author(s):  
Reena Sen ◽  
Cristina E. González-Espinoza ◽  
Alexander Zech ◽  
Andreas Dreuw ◽  
Tomasz A. Wesolowski
Keyword(s):  
Embedding Theory

scholarly journals Wavelength-Dependent Nonlinear Absorption in Palladium Nanoparticles

2021 ◽  
Vol 11 (4) ◽  
pp. 1640
Author(s):  
Chunyu Chen ◽  
Jun Wang ◽  
Yachen Gao
Keyword(s):  
Surface Plasmon Resonance ◽  
Excitation Energy ◽  
Systematic Study ◽  
Nonlinear Absorption ◽  
Palladium Nanoparticles ◽  
Excitation Wavelength ◽  
Saturated Absorption ◽  
Multi Wavelength ◽  
Resonant Region ◽  
Absorption Characteristics

This paper aims to study the nonlinear absorption characteristics of palladium nanoparticles (PdNPs) at off-resonant wavelengths. For this purpose, multi-wavelength (500–650 nm) nanosecond Z-scan technique was used. The experimental results indicate that saturated absorption (SA) and the transition from SA to reverse saturated absorption (RSA) can occur, and depends on the excitation wavelength and energy. When the excitation wavelength is constant, with the increase of excitation energy, PdNPs change from SA to RSA. When the excitation energy is constant, with the excitation wavelength approaching surface plasmon resonance (SPR), PdNPs change from SA to RSA. This phenomenon of SA and RSA under multi-wavelength excitation in the off-resonant region provides a supplement for the systematic study of the nonlinear absorption of PdNPs.

scholarly journals Chemical in‐depth analysis of (Ca/Sr)F 2 core–shell like nanoparticles by X‐ray photoelectron spectroscopy with tunable excitation energy

2021 ◽  
Vol 53 (5) ◽  
pp. 494-508
Author(s):  
Anja Müller ◽  
Thoralf Krahl ◽  
Jörg Radnik ◽  
Andreas Wagner ◽  
Carsten Kreyenschulte ◽  
...  
Keyword(s):  
Excitation Energy ◽  
Photoelectron Spectroscopy ◽  
Core Shell ◽  
X Ray ◽  
Depth Analysis
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