Search results for "Luminescence"

The study of time-resolved absorption and luminescence in PbWO4 crystals

2000

Abstract The transient absorption and luminescence under pulsed electron beam excitation were studied for undoped and La3+ doped PbWO4 crystals. The absorption band at ∼1.0 eV is suggested to be due to self-trapped electrons and the absorption band at 3.5 eV may be due to self-trapped holes. The formation of luminescence centers via electron–hole recombination is affected by La3+ in doped crystals. The large fraction of electrons and holes undergoes thermostimulated recombination within geminate pairs and the spatial separation of geminate pairs components is important in recombination process. The intrinsic (blue) luminescence arises in this recombination. The mechanism of La3+ influence o…

Irradiation Effects in Optical Fibers

2010

Intrinsic and extrinsic optical fiber-based sensors are promising devices to be used in very different and complex environments, by their very nature: capabilities to work under electromagnetic fields; possibility to carry multiplexed signals (time, wavelength multiplexing); small size and low mass; ability to handle multi-parameter measurements in distributed configuration; possibility to monitor sites far away from the controller. In the case of the optical fibers, the possibility to be incorporated into various types of sensors and actuators, free of additional hazards (i.e. fire, explosion), made them promising candidates to operate in adverse conditions as those required by space appli…

Dependence of the emission properties of the germanium lone pair center on Ge doping of silica

2011

We present an experimental investigation regarding the changes induced by the Ge doping level on the emission profile of the germanium lone pair center (GLPC) in Ge doped silica. The investigated samples have been produced by the sol-gel method and by plasma-activated chemical vapor deposition and have doping levels up to 20% by weight. The recorded photoluminescence spectra show that the GLPC emission profile is the same when the Ge content is lower than ∼ 1% by weight, whereas it changes for higher doping levels. We have also performed Raman scattering measurements that show the decrease of the D1 Raman band at 490 cm( - 1) when the Ge content is higher than 1% by weight. The data suggest…

Ligand-Centred Fluorescence and Electronic Relaxation Cascade at Vibrational Time Scales in Transition-Metal Complexes

2015

Using femtosecond-resolved photoluminescence up-conversion, we report the observation of the fluorescence of the high-lying ligand-centered (LC) electronic state upon 266 nm excitation of an iridium complex, Ir(ppy)(3), with a lifetime of 70 +/- 10 fs. It is accompanied by a simultaneous emission of all lower-lying electronic states, except the lowest triplet metal-to-ligand charge-transfer ((MLCT)-M-3) state that shows a rise on the same time scale. Thus, we observe the departure, the intermediate steps, and the arrival of the relaxation cascade spanning similar to 1.6 eV from the (LC)-L-1 state to the lowest 3MLCT state, which then yields the long-lived luminescence of the molecule. This …

Optical transitions associated with non bridging oxygen hole centers in irradiated silica

2005

Pt(II) and Pd(II)-assisted coupling of nitriles and 1,3-diiminoisoindoline : Synthesis and luminescence properties of (1,3,5,7,9-pentaazanona-1,3,6,8…

2017

Treatment of trans-[PtCl2(NCR)2] 1 (R = Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HCdouble bond; length as m-dashO)C6H4 (1e), p-O2NC6H4CH2 (1f)) with 1,3-diiminoisoindoline HNdouble bond; length as m-dashCC6H4C(NH)double bond; length as m-dashNH 2 gives access to the corresponding (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes [PtCl{NHdouble bond; length as m-dashC(R)Ndouble bond; length as m-dashC(C6H4)NCdouble bond; length as m-dashNC(R)double bond; length as m-dashNH}] 3a–f, in good yields (65–70%). The reaction of trans-[PdCl2(NCMe)2] 4a with 2 furnishes (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pd(II) complex [PdCl{NHdouble bond; length as m-dashC(Me)Ndouble bond…

Deterministic Modification of CVD Grown Monolayer MoS2 with Optical Pulses

2021

| openaire: EC/H2020/820423/EU//S2QUIP | openaire: EC/H2020/834742/EU//ATOP Transition metal dichalcogenide monolayers have demonstrated a number of exquisite optical and electrical properties. Here, the authors report the optical modification of topographical and optical properties of monolayer MoS2 with femtosecond pulses under an inert atmosphere. A formation of three-dimensional structures on monolayer MoS2 with tunable height up to ≈20 nm is demonstrated. In contrast to unmodified monolayer MoS2, these optically modified structures show significantly different optical properties, such as lower photoluminescence intensity and longer fluorescence lifetime. The results suggest a novel way…

Optical Fiber Based Dosimeter Data From RADEF Pulsed Electron Beams - Oscilloscope Traces

2021

These data are from tests of fiber optic based dosimetry systems. The purpose of the collected data is to use it for characterizing the different tested samples responses against pulsed electron radiation, for different electron bunch sizes. The tested samples are sol-gel silica glass rods doped with Ce, Cu, or Gd ions, making the rods radioluminescent. The samples were connected to a multimode pure-silica core optical fiber, which transported the radiation induced luminescence (RIL) to a photomultiplier tube (PMT) with an optical band pass filter in front of it. The samples were subject to a pulsed 20 MeV electron beam. The resulting output pulses from the PMT from the induced RIL light we…

Oxidation of silicon nanoparticles produced by ns laser ablation in liquids

2014

The investigation of nanoparticles produced by ns pulsed Nd:YAG laser ablation of silicon in liquids is reported. Combined characterization by morphological and structural techniques shows that these nanoparticles have a mean diameter of ~3 nm and a core-shell structure consisting of a Si-nanocrystal surrounded by a layer of oxidized Si. Time resolved luminescence spectra evidence visible and UV emissions: a broad band around 1.9 eV originates from Si-nanocrystals, while two bands centered at 2.7 eV and 4.4 eV are associated with oxygen deficient centers in the SiO2 shell.

Asymmetric Ring Opening in Tetrazine‐based Ligand Affording a Tetranuclear Opto‐Magnetic Ytterbium Complex

2021

We report the formation of a tetranuclear lanthanide cluster, [Yb 4 (bpzch) 2 (fod) 10 ] ( 1 ), which occurs from a serendipitous ring opening of the functionalized tetrazine bridging ligand, bpztz (3,6‐dipyrazin‐2‐yl‐1,2,4,5‐tetrazine) upon reacting with Yb(fod) 3 (fod ‐ = 6,6,7,7,8,8,8‐heptafluoro‐2,2‐dimethyl‐3,5‐octandionate). Compound 1 was structurally elucidated via single‐crystal X‐ray crystallography and subsequently magnetically and spectroscopically characterized to analyse its magnetisation dynamics and its luminescence behaviour. Computational studies validate the observed M J energy levels attained by spectroscopy and provides a clearer picture of the slow relaxation of the ma…