A measurement of the mean electronic excitation energy of liquid xenon

Detectors using liquid xenon as target are widely deployed in rare event searches. Conclusions on the interacting particle rely on a precise reconstruction of the deposited energy which requires calibrations of the energy scale of the detector by means of radioactive sources. However, a microscopic calibration, i.e. the translation from the number of excitation quanta into deposited energy, also necessitates good knowledge of the energy required to produce single scintillation photons or ionisation electrons in liquid xenon. The sum of these excitation quanta is directly proportional to the deposited energy in the target. The proportionality constant is the mean excitation energy and is commonly known as W-value. Here we present a measurement of the W-value with electronic recoil interactions in a small dual-phase xenon time projection chamber with a hybrid (photomultiplier tube and silicon photomultipliers) photosensor configuration. Our result is based on calibrations at $$\mathcal {O}(1{-}10\,{\hbox {keV}})$$ O ( 1 - 10 keV ) with internal $${^{37}\hbox {Ar}}$$ 37 Ar and $${^{83\text {m}}\hbox {Kr}}$$ 83 m Kr sources and single electron events. We obtain a value of $$W={11.5}{} \, ^{+0.2}_{-0.3} \, \mathrm {(syst.)} \, \hbox {eV}$$ W = 11.5 - 0.3 + 0.2 ( syst . ) eV , with negligible statistical uncertainty, which is lower than previously measured at these energies. If further confirmed, our result will be relevant for modelling the absolute response of liquid xenon detectors to particle interactions.

Hybrid Complexes of Photosensitizers with Luminescent Nanoparticles: Design of the Structure

Increasing the efficiency of the photodynamic action of the dyes used in photodynamic therapy is crucial in the field of modern biomedicine. There are two main approaches used to increase the efficiency of photosensitizers. The first one is targeted delivery to the object of photodynamic action, while the second one is increasing the absorption capacity of the molecule. Both approaches can be implemented by producing dyenanoparticle conjugates. In this review, we focus on the features of the latter approach, when nanoparticles act as a light-harvesting agent and nonradiatively transfer the electronic excitation energy to a photosensitizer molecule. We will consider the hybrid photosensitizerquantum dot complexes with energy transfer occurring according to the inductive-resonance mechanism as an example. The principle consisting in optimizing the design of hybrid complexes is proposed after an analysis of the published data; the parameters affecting the efficiency of energy transfer and the generation of reactive oxygen species in such systems are described.

Radiolysis of transformer oil in presence of trichlorbenzen and nano-γ-Al2O3

In this work, a comparative study of the kinetics of changes in the pH indicator, the formation of H2O2 and CO2 depending on the absorbed dose at the radiolysis of TCB containing transformer oil in the presence and without nano-γ-Al2O3 under the action of γ radiation was carried out. During radiolysis of both systems (TСB + transformer oil and TСB + transformer oil + 0.1 g of nano-γ-Al2O3), the radiation-chemical yield of CO2 decreases with an increase in the initial concentration of TCB, although at the presence of nano-particles, the values of the radiation-chemical riels of CO2 become less. Unlike CO2, the radiation-chemical yields of H2O2 increase with an increase in the initial concentration of TCB, but their values are less in the presence of nano-γ-Al2O3. The results obtained are explained by the reactions of active particles, radiolysis of the main components of transformer oil, such as hydrogen atoms and hydrocarbon radicals with TCB and dissolved oxygen molecules. In addition, there is a transfer of electronic excitation energy from alkane and cycloalkane molecules to aromatic hydrocarbon molecules. The effect of nano-γ-Al2O3 on the radiolysis of the mixture is discussed on the basis of the reaction of electron and hole centers with the molecules of the components of the irradiated mixture.

The Peculiarities of Singlet Electronic Excitation Energy Transfer Processes in Alq3 Films

The absorption and luminescence of new boron-containing dyes in two-component films of Alq3 (matrix)-dye(impurity) (obtained by the method of thermal vacuum deposition) are studied. The comparison of the spectra of absorption, fluorescence, and fluorescence excitation of a dyes in one-component solutions and double-component films shows the existence of the effective electronic excitation energy transfer (EEET) from the matrix to dye molecules. Time-resolved spectra of two-component films also manifest strong EEET in these systems. For the estimation of the average exciton spreading length in Alq3 films, the diffusion model of the motion of singlet excitons is used. The diffusion coefficient is evaluated using time-resolved spectroscopy. The optimum concentrations of dyes in a light-emitting layer of OLED are evaluated based on experimental data and the used model of EEET.

Разнолигандные комплексные соединения европия (III) с o-метоксибензойной кислотой и фосфорсодержащими нейтральными лигандами

The luminescent coordination multi-ligand compounds of europium (III) with o-methoxybenzoic acid and island-containing phosphorus-containing neutral ligands of the composition Eu (MOBA) 3 • 3Н2О and Eu (MOBA) 3 • L, where MOBA is o-methoxybenzoic acid, D is hmpa (D hexamethylphosphoric triamide), tppo (triphenylphosphine oxide), Et6pa (hexaethylphosphotriamide). The composition, structure, and thermal properties of complex multi-ligand compounds of europium (III) were studied. It was shown that during thermolysis, detachment of a neutral ligand molecule occurs in one stage with an endothermic effect, complex compounds are stable up to 280 С.Based on the data of IR spectroscopy, it was found that in the europium (III) o-methoxybenzoates, the o-methoxybenzoic acid is coordinated to the europium (III) o-methoxybenzoic ion in a bidentate manner. The low luminescence intensity of multi-ligand europium (III) compounds is explained by the inefficient transfer of electronic excitation energy from o-methoxybenzoic acid and phosphorus-containing neutral ligands to the europium ion.

FLUORESCENT PROPERTIES OF PHENYL - CONTAINING ISOMERS OF PALLADIUM COMPLEXES OF OCTAETHYLPORPHIN IN ACETONITRILE

The fluorimetric measurements of the acetonitrile solutions of palladium complexes of the octaethylporphyrin, 5,10- biphenyl octaethylporphyrin and 5,15-biphenyl octaethylporphyrin at 293 K were performed. Tetraphenylporfin was used in toluene as standards. It was determined that the studied compounds differ in the architecture of peripheral substitution, and as a result in molecular conformation and symmetry, which determine the rates of intramolecular processes of deactivation of electronic excitation energy. It was established that the introduction of two phenyl fragments into the meso-positions of the tetrapyrrole macrocycle of the octaethylporphyrin molecule markedly changes the spectral-luminescent properties of their palladium complexes. The compound with the adjacent arrangement of phenyl fragments of 5,10-diphenylctaethylporphyrin is characterized by concentrated steric effects in the region of one quadrant of the macrocycle containing two phenyl groups and the pyrrole fragment located between them. This arrangement of phenyl fragments leads to the formation of an asymmetrically distorted saddle-shaped conformer, as evidenced by the bathochromic shift of the bands in the electronic absorption spectrum by 495 cm–1. The quantum yield of S1→S0 fluorescence decreases slightly to 4.6·10-3, which is explained by the formation of a new competing non-radiative deactivation channel — the internal S1→S0 conversion, which is characteristic of distorted saddle-shaped macrocycle. When phenyl groups at opposite meso-positions of the 5.15-diphenyl octaethylporphyrin macrocycle flanked by alkyl groups in the Cb positions of the pyrrole rings, a conformer is formed with a macrocycle elongated along the Cm-Cm axis. This is probably due to the stricter molecular structure of this conformer compared to palladium octaethylporphyrin and the absence of conformational dynamics in the S1 excited state. As a result, the bathochromic shift of the bands in the electronic absorption spectrum of 5.15 – diphenyl octaethylporphyrin is less than 100 cm-1 and the quantum yield of S1→S0 fluorescence is almost equal to the quantum yield of the palladium complex of octaethylporphyrin - 5.4·10-3, which is probably due to the low non-radiative internal S1→S0 conversion for the 5.15-diphenyl octaethylporphyrin compared to the 5.10-diphenyl octaethylporphyrin.