scholarly journals Photophysics and spectroscopy of metal particles

2000 ◽  
Vol 72 (1-2) ◽  
pp. 189-197 ◽  
Author(s):  
José H. Hodak ◽  
Arnim Henglein ◽  
Gregory V. Hartland
Keyword(s):  
Transient Absorption ◽  
Classical Mechanics ◽  
Transient Absorption Spectroscopy ◽  
Metal Particles ◽  
Characteristic Time Scale ◽  
Phonon Coupling ◽  
Particle Volume ◽  
Plasmon Band ◽  
Free Electron Density ◽  
Electron Phonon Coupling

This paper describes our recent work using ultrafast laser spectroscopy to examine the fundamental properties of metal particles. Two studies are presented. First, the characteristic time scale for electron-phonon coupling in Au particles with sizes between 2 and 120 nm has been examined by bleach recovery measurements. These experiments show that the coupling between the electrons and phonons is independent of particle size, to within the signal-to-noise of our experiments. We have also used transient absorption spectroscopy to examine the low-frequency "breathing" modes of the Au particles. These modes are impulsively excited by the rapid lattice heating that accompanies electron-phonon coupling. The breathing motion contributes to the transient absorption signal because the position of the plasmon band depends on the free electron density and, thus, the particle volume. The measured frequencies are inversely proportional to the radius, and almost exactly match the predictions of classical mechanics calculations for Au.

scholarly journals Anomalous phonon relaxation in Au333(SR)79 nanoparticles with nascent plasmons

2019 ◽  
Vol 116 (27) ◽  
pp. 13215-13220 ◽  
Author(s):  
Tatsuya Higaki ◽  
Meng Zhou ◽  
Guiying He ◽  
Stephen D. House ◽  
Matthew Y. Sfeir ◽  
...  
Keyword(s):  
Relaxation Process ◽  
Transient Absorption ◽  
Quantum Effect ◽  
Transient Absorption Spectroscopy ◽  
Phonon Coupling ◽  
Size Regime ◽  
Femtosecond Transient Absorption ◽  
Electron Phonon Coupling ◽  
Future Work ◽  
Broad Interest

Research on plasmons of gold nanoparticles has gained broad interest in nanoscience. However, ultrasmall sizes near the metal-to-nonmetal transition regime have not been explored until recently due to major synthetic difficulties. Herein, intriguing electron dynamics in this size regime is observed in atomically precise Au333(SR)79 nanoparticles. Femtosecond transient-absorption spectroscopy reveals an unprecedented relaxation process of 4–5 ps—a fast phonon–phonon relaxation process, together with electron–phonon coupling (∼1 ps) and normal phonon–phonon coupling (>100 ps) processes. Three types of –R capped Au333(SR)79 all exhibit two plasmon-bleaching signals independent of the –R group as well as solvent, indicating plasmon splitting and quantum effect in the ultrasmall core of Au333(SR)79. This work is expected to stimulate future work on the transition-size regime of nanometals and discovery of behavior of nascent plasmons.

Difference in hot carrier cooling rate between Langmuir–Blodgett and drop cast PbS QD films due to strong electron–phonon coupling

Nanoscale ◽  
2017 ◽  
Vol 9 (43) ◽  
pp. 17133-17142 ◽  
Author(s):  
Wenkai Cao ◽  
Lin Yuan ◽  
Rob Patterson ◽  
Xiaoming Wen ◽  
Patrick C. Tapping ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Phonon Coupling ◽  
Lead Sulphide ◽  
Strong Electron ◽  
Hot Carrier ◽  
Langmuir Blodgett ◽  
Femtosecond Transient Absorption ◽  
Electron Phonon Coupling ◽  
Langmuir Blodgett Films

The carrier dynamics of lead sulphide quantum dot (PbS QD) drop cast films and closely packed ordered Langmuir–Blodgett films are studied with ultra-fast femtosecond transient absorption spectroscopy.

Ultrafast Transient Absorption Spectroscopy Investigations of Excited State Dynamics in SWNT/Polymer Composites

2004 ◽  
Vol 858 ◽  
Author(s):  
David J. Styers-Barnett ◽  
Steven P. Ellison ◽  
Cheol Park ◽  
Kristopher E. Wise ◽  
John M. Papanikolas
Keyword(s):  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Hot Electron ◽  
Plasmon Band ◽  
Near Ir ◽  
Spectral Shifts ◽  
Femtosecond Transient Absorption ◽  
Transient Spectra ◽  
Walled Carbon Nanotubes

ABSTRACTWavelength-resolved femtosecond transient absorption spectroscopy is used to follow the electronic dynamics of single-walled carbon nanotubes in polymers following visible and near IR photoexcitation. Electron-hole (e-h) pairs give rise to sharp features in the transient spectra that decay in amplitude and exhibit rapid spectral shifts. The decay reflects (e-h) recombination on both short (1.3 ps) and long (35 ps) time scales. Transient spectra also exhibit a broad photobleach at early times that arises from the cooling of a hot electron gas created via excitation at the red edge of a π-plasmon band.

scholarly journals Direct determination of mode-projected electron-phonon coupling in the time domain

Science ◽  
2019 ◽  
Vol 366 (6470) ◽  
pp. 1231-1236 ◽  
Author(s):  
M. X. Na ◽  
A. K. Mills ◽  
F. Boschini ◽  
M. Michiardi ◽  
B. Nosarzewski ◽  
...  
Keyword(s):  
Time Domain ◽  
Phonon Scattering ◽  
Direct Determination ◽  
Spectral Weight ◽  
Characteristic Time Scale ◽  
Phonon Coupling ◽  
Strongly Coupled ◽  
Nonthermal Electrons ◽  
Electron Phonon Coupling ◽  
The Time Domain

Ultrafast spectroscopies have become an important tool for elucidating the microscopic description and dynamical properties of quantum materials. In particular, by tracking the dynamics of nonthermal electrons, a material’s dominant scattering processes can be revealed. Here, we present a method for extracting the electron-phonon coupling strength in the time domain, using time- and angle-resolved photoemission spectroscopy (TR-ARPES). This method is demonstrated in graphite, where we investigate the dynamics of photoinjected electrons at the K¯ point, detecting quantized energy-loss processes that correspond to the emission of strongly coupled optical phonons. We show that the observed characteristic time scale for spectral weight transfer mediated by phonon-scattering processes allows for the direct quantitative extraction of electron-phonon matrix elements for specific modes.

Pronounced exciton and coherent phonon dynamics in BiI3

2018 ◽  
Vol 20 (16) ◽  
pp. 10677-10685 ◽  
Author(s):  
Mirko Scholz ◽  
Kawon Oum ◽  
Thomas Lenzer
Keyword(s):  
Transient Absorption ◽  
Coherent Phonon ◽  
Phonon Coupling ◽  
Strong Electron ◽  
Electron Phonon Coupling ◽  
Phonon Dynamics

Long-lived coherent oscillations in transient absorption signals of BiI3 suggest strong electron–phonon coupling in this material for photovoltaics.

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.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

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