Search results for "FAST"

Luminescence Center Excited State Absorption in Calcium and Zinc Tungsates

2002

The tungstate crystals are well known scintillators. The mechanism of luminescence center formation and the luminescence center model are under discussion today. The results of time-resolved spectroscopy of luminescence center in ZnWO4 and CaWO4 in wide temperature regions was presented. The luminescence and induced absorption under pulsed electron beam excitation (pulse duration 10 ns, 0.26 MeV) were studied. The experimental equipment used allows one to obtain the transient absorption spectra, luminescence decay kinetics and transient absorption relaxation times.

Real-time observation of the intravalley spin-flip process in single-layer WS2

2019

We use helicity-resolved transient absorption spectroscopy to track intravalley scattering dynamics in monolayer WS2. We find that spin-polarized carriers scatter from upper to lower conduction band by reversing their spin orientation on a sub-ps timescale.

Transient absorption and luminescence of LiNbO3 and KNbO3

2001

Abstract The results of time-resolved optical absorption spectra in congruent and stoichiometric LiNbO3 as well as KNbO3 crystals are reported. The role of different polaron types in transient absoiption and luminescence spectra and decay kinetics are discussed.

Luminescence and Transient Optical Absorption in CdWO<sub>4</sub>

1997

Ultrafast spectroscopic investigation on fluorescent carbon nanodots: the role of passivation.

2019

Disentangling the respective roles of the surface and core structures in the photocycle of carbon nanodots is a critical open problem in carbon nanoscience. While the need of passivating carbon dot surfaces to obtain efficiently emitting nanoparticles is very well-known in the literature, it is unclear if passivation introduces entirely new surface emitting states, or if it stabilizes existing states making them fluorescent. In this multi-technique femtosecond spectroscopy study, the relaxation dynamics of non-luminescent (non-passivated) carbon dots are directly compared with their luminescent (passivated) counterparts. Non-passivated dots are found to host emissive states, albeit very sho…

Luminescence and EPR spectroscopy of neutron-irradiated single crystals of magnesium aluminium spinel

2016

Abstract Neutron irradiated single crystals of stoichiometric MgAl 2 O 4 and MgAl 2 O 4 :Mn 2+ (0.15 wt. %) were studied using the methods of luminescence spectroscopy and versions of electron paramagnetic resonance. In stoichiometric MgAl 2 O 4 :Mn 2+ single crystals, the transition of a part of manganese impurity ions from tetrahedral to octahedral coordination, caused by irradiation with fast fission neutrons, is detected using photoluminescence spectra. This fact confirms the partial inversion of a normal spinel due to neutron-irradiation. Using pulse EPR technique it is shown that an electron in the field of oxygen vacancy (i.e. from neutron-irradiation induced F + centres, which are s…

Low-temperature studies of Cr 3+ ions in natural and neutron-irradiated g-Al spinel

2020

This study was supported by a grant from Latvian Council of Science (agreement No. LZP-2018/1-0214).

Photodynamics at the CdSe Quantum Dot–Perylene Diimide Interface: Unraveling the Excitation Energy and Electron Transfer Pathways

2021

Excitation energy and charge transfer processes in perylene diimide dye–CdSe quantum dot complexes have been studied by femtosecond transient absorption spectroscopy. After excitation of the quantu...

Recent Progress in the Development of Composite Membranes Based on Polybenzimidazole for High Temperature Proton Exchange Membrane (PEM) Fuel Cell Ap…

2020

[EN] The rapid increasing of the population in combination with the emergence of new energy-consuming technologies has risen worldwide total energy consumption towards unprecedent values. Furthermore, fossil fuel reserves are running out very quickly and the polluting greenhouse gases emitted during their utilization need to be reduced. In this scenario, a few alternative energy sources have been proposed and, among these, proton exchange membrane (PEM) fuel cells are promising. Recently, polybenzimidazole-based polymers, featuring high chemical and thermal stability, in combination with fillers that can regulate the proton mobility, have attracted tremendous attention for their roles as PE…

Relaxation of electronic excitations in LiNbO3crystals

2001

Transient absorption both in stoichiometric and Mg doped congruent LiNbO was observed after pulsed electron beam excitation. The luminescence spectra and decay kinetics in these materials show different excitonic relaxation possibilities. The dependence on sample stoichiometry is also discussed.