Ultrafast Radiative Relaxation Processes in Multication Cross-Luminescence Materials

The group-theoretical analysis of polymethine dyes (PMD) showed that relaxation processes between the states S3 and S1 are forbidden, either by radiation or by internal conversion. From the state S3, only transition to the ground state of the molecule is possible. Since the experimental data state that the quantum yield of S3 ⟶ S0 fluorescence does not exceed 1%, it is indicated that the internal conversion rate can be 2 orders of magnitude higher than the radiative relaxation rate of the molecule. Concerning the reasons for the appearance of fluorescence from the higher excited states of molecules, it can be asserted that the necessary condition for the appearance of S3 ⟶ S0 fluorescence is the absence of S0 ⟶ S1(v)-absorption in the region of the S0 ⟶ S3 transition. The sufficient condition is the corresponding symmetry of the excited states, which imposes a prohibition on the S3 ⟶ S1 relaxation process.

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Structure and excited state properties of multiporphyrin arrays formed by supramolecular design

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424603000914 ◽

2003 ◽

Vol 07 (11) ◽

pp. 731-754 ◽

Cited By ~ 13

Author(s):

Eduard I. Zenkevich ◽

Christian von Borczyskowski ◽

Alexander M. Shulga

Keyword(s):

Excited State ◽

Photoinduced Electron Transfer ◽

Spectral Properties ◽

Photophysical Properties ◽

Covalent Binding ◽

Relaxation Processes ◽

Radiative Relaxation ◽

Time Resolved ◽

Chemical Dimers ◽

Femtosecond Time Scale

Structurally defined nanoscale self-assembled multiporphyrin arrays of variable geo-metry and composition (up to eight tetrapyrrole macrocycles) have been formed via two-fold extra-ligation in solutions at 77-293 K. The array formation is based on non-covalent binding interactions of the phenyl bridged Zn octaethylporphyrin chemical dimers or trimers, ( ZnOEP )2 Ph or ( ZnOEP )3 Ph 2, with di- and tetrapyridyl substituted tetrapyrrole extra-ligands (porphyrin, pentafluorophenyl substituted porphyrin, Cu porphyrin, tetrahydroporphyrin). Using steady-state and time-resolved measurements, spectral properties as well as pathways and dynamics of non-radiative relaxation processes (energy migration, photoinduced electron transfer, exchange d-π effects, realized in nano-femtosecond time scale) have been studied in these complexes upon variation of the composition, mutual geometry, redox and photophysical properties of interacting subunits as well as on the tempera-ture and polarity of surrounding.

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Non-radiative relaxation processes of the Pr3+ ion in solids

Journal of Physics and Chemistry of Solids ◽

10.1016/0022-3697(94)00183-9 ◽

1995 ◽

Vol 56 (5) ◽

pp. 673-685 ◽

Cited By ~ 117

Author(s):

C. De Mello Donegá ◽

A. Meijerink ◽

G. Blasse

Keyword(s):

Relaxation Processes ◽

Radiative Relaxation

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Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

The Journal of Physical Chemistry A ◽

10.1021/jp034804n ◽

2003 ◽

Vol 107 (33) ◽

pp. 6457-6463 ◽

Cited By ~ 3

Author(s):

David B. Pedersen ◽

Marek Z. Zgierski ◽

Benoit Simard

Keyword(s):

Gas Phase ◽

Relaxation Processes ◽

Radiative Relaxation ◽

Dna Base

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Theoretical aspects of transient temperature on cubic crystal surface in a photoacoustic effect

Bulletin of the Karaganda University Physics Series ◽

10.31489/2020ph3/73-79 ◽

2020 ◽

Vol 99 (3) ◽

pp. 73-79

Author(s):

A.P. Sarode ◽

◽

O.H. Mahajan ◽

Keyword(s):

Integral Transform ◽

Crystal Surface ◽

Solid Sample ◽

Transient Temperature ◽

Relaxation Processes ◽

Photoacoustic Cell ◽

Radiative Relaxation ◽

Cubic Crystal ◽

Photoacoustic Effect ◽

Translational Temperature

In photoacoustic effect, the solid sample absorbs a fraction of the radiation falling upon it and excitation process occurs. The type of excitation depends on the energy of the incident radiation. The relaxation processes, which are also popularly known as non-radiative de-excitation processes generally take place. The light – matter interaction is responsible for the generation of heat within the solid sample. The temperature of the sample changes due to absorption and non-radiative relaxation by the atoms. The pressure fluctuations will be generated due to the heating and cooling of the sample. Today, crystalline solids are widely studied due to their wide scientific and industrial applications. Temperature is one of the important parameter to be studied regarding artificial preparation of large crystals. In this paper, transient translational temperature on the surface of a homogeneous isotropic cubic crystal kept in a photoacoustic cell is calculated theoretically. For a simple cubic homogeneous crystal kept in a photoacoustic cell, an airy stress function is determined based on laser interaction with surface of the crystal. By applying the finite Marchi-Fasulo integral transform method within the crystal size limitations, transient translational temperature is exactly determined.

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Multiband emission from single β-NaYF4(Yb,Er) nanoparticles at high excitation power densities and comparison to ensemble studies

Nano Research ◽

10.1007/s12274-021-3350-y ◽

2021 ◽

Author(s):

Florian Frenzel ◽

Christian Würth ◽

Oleksii Dukhno ◽

Frédéric Przybilla ◽

Lisa M. Wiesholler ◽

...

Keyword(s):

Energy Transfer ◽

Single Particle ◽

Near Infrared ◽

Upconversion Luminescence ◽

Excited State Absorption ◽

High Energy ◽

Excitation Power ◽

Relaxation Processes ◽

Excitation Power Density ◽

Radiative Relaxation

AbstractEnsemble and single particle studies of the excitation power density (P)-dependent upconversion luminescence (UCL) of core and core-shell β-NaYF4:Yb,Er upconversion nanoparticles (UCNPs) doped with 20% Yb3+ and 1% or 3% Er3+ performed over a P regime of 6 orders of magnitude reveal an increasing contribution of the emission from high energy Er3+ levels at P > 1 kW/cm2. This changes the overall emission color from initially green over yellow to white. While initially the green and with increasing P the red emission dominate in ensemble measurements at P < 1 kW/cm2, the increasing population of higher Er3+ energy levels by multiphotonic processes at higher P in single particle studies results in a multitude of emission bands in the ultraviolet/visible/near infrared (UV/vis/NIR) accompanied by a decreased contribution of the red luminescence. Based upon a thorough analysis of the P-dependence of UCL, the emission bands activated at high P were grouped and assigned to 2–3, 3–4, and 4 photonic processes involving energy transfer (ET), excited-state absorption (ESA), cross-relaxation (CR), back energy transfer (BET), and non-radiative relaxation processes (nRP). This underlines the P-tunability of UCNP brightness and color and highlights the potential of P-dependent measurements for mechanistic studies required to manifest the population pathways of the different Er3+ levels.

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