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Ytterbium-doped single crystals of the high-temperature hexagonal sodium sulphate modification are grown by the Czochralski method. It is found by energy dispersive analysis that the crystallisation occurs congruently. The Yb : Na2SO4 crystals have additional (with respect to Yb3+ ions) absorption bands in the regions of 650, 850 and 1150 nm, which obviously belong to colour centres. The luminescence spectrum of the Yb : Na2SO4 single crystal noticeably differs from the luminescence spectrum of Yb : YAG crystals by the presence of a broad band without a prominent peak. The luminescence decay curve for the powder is single-exponential with a time constant of 1175 μs, which is somewhat larger than that for the Yb : YAG crystal. The lifetime of the ytterbium excited state does not change during storage of the samples in air for a week.

The 2p photoionization of sodium atoms from the initial states 2p 63p 1/2,3/2 have been investigated, with special emphasis placed on the relaxation and correlation effects. To understand the details of the spectra, a series of ab initio calculations based on the multi-configuration Dirac–Fock method have been performed. Theoretical predictions have been compared with the high-resolution spectra measured using a synchrotron radiation source, and suitable agreement between experiment and theory has enabled the identification of fine-structure spectra. The prominent influence of the relaxation and correlation effects on the photoelectron spectra has been analysed according to the detailed calculations.

The fluorescence mechanism of HBT-HBZ is investigated in this work. A fluorescent probe is used to detect HClO content in living cells and tap water, and its structure after oxidation by HClO (HBT-ClO) is discussed based on the density functional theory (DFT) and time-dependent density functional theory (TDDFT). At the same time, the influence of the probe conformation and the proton transfer site within the excited state molecule on the fluorescence mechanism are revealed. Combined with infrared vibrational spectra and atoms-in-molecules theory, the strength of intramolecular hydrogen bonds in HBT-HBZ and HBT-ClO and their isomers are demonstrated qualitatively. The relationship between the strength of intramolecular hydrogen bonds and dipole moments is discussed. The potential energy curves demonstrate the feasibility of intramolecular proton transfer. The weak fluorescence phenomenon of HBT-HBZ in solution is quantitatively explained by analyzing the frontier molecular orbital and hole electron caused by charge separation. Moreover, when strong cyan fluorescence occurs in solution, the corresponding molecular structure should be HBT-ClO(T). The influence of the intramolecular hydrogen bond formation site on the molecule as a whole is also investigated by electrostatic potential analysis.

Photocatalytic conversion of carbon dioxide into fuels and valuable chemicals is a promising method for carbon neutralization and solving environmental problems. Through a simple thermal-oxidative exfoliation method, the O element was doped while exfoliated bulk g-C3N4 into ultrathin structure g-C3N4. Benefitting from the ultrathin structure of g-C3N4, the larger surface area and shorter electrons migration distance effectively improve the CO2 reduction efficiency. In addition, density functional thory computation proves that O element doping introduces new impurity energy levels, which making electrons easier to be excited. The prepared photocatalyst reduction of CO2 to CO (116 μmol g−1 h−1) and CH4 (47 μmol g−1 h−1).

Nitrogen is a very common element, comprising approximately 78% of Earth’s atmosphere, and is an important component of various electronic devices while also being essential for life. However, it is challenging to directly utilize dinitrogen because of the highly stable triple bond in this molecule. The present review examines the use of non-equilibrium plasmas to generate controlled electron impacts as a means of generating reactive nitrogen species (RNS) with high internal energy values and extremely short lifetimes. These species include ground state nitrogen atoms, excited nitrogen atoms, etc. RNS can subsequently react with oxygen and/or hydrogen to generate new highly reactive compounds and can also be used to control various cell functions and create new functional materials. Herein, plasma-processing methods intended to provide RNS serving as short-lived precursors for a range of applications are examined in detail.

Based on a high level ab initio calculation which is carried out with the multireference configuration interaction method under the aug-cc-pVXZ (AVXZ) basis sets, X = T, Q, 5, the accurate potential energy curves (PECs) of the ground state X Σ g + 1 and the first excited state A Σ u + 1 of Li2 are constructed. By fitting the ab initio potential energy points with the Murrell–Sorbie potential function, the analytic potential energy functions (APEFs) are obtained. The molecular bond length at the equilibrium (R e ), the potential well depth (D e ), and the spectroscopic constants (B e , ω e , α e , and ω e χ e ) for the X Σ g + 1 state and the A Σ u + 1 state are deduced from the APEFs. The vibrational energy levels of the two electronic states are obtained by solving the time-independent Schrödinger equation with the Fourier grid Hamiltonian method. All the spectroscopic constants and the vibrational levels agree well with the experimental results. The Franck–Condon factors (FCFs) corresponding to the transitions from the vibrational level (v′ = 0) of the ground state to the vibrational levels (v″ = 0–74) of the first excited state have been calculated. The FCF for the vibronic transition of A Σ u + 1 (v″ = 0) ← X Σ g + 1 (v′ = 0) is the strongest. These PECs and corresponding spectroscopic constants provide reliable theoretical references to both the spectroscopic and the molecular dynamic studies of the Li2 dimer.

Several transition metal dichalcogenides (TMDs) can be exfoliated to produce nearly two-dimensional (2D) semiconductor layers supporting robust excitons with non-hydrogenic Rydberg series of states. Black phosphorus (BP) can also be layered to create a nearly 2D material with interesting properties including its pronounced in-plane anisotropy that influences, in particular, exciton states making them different from those in other 2D semiconductors. We apply the Rayleigh–Ritz variational method to evaluate the energies and approximate the wavefunctions of the ground and lowest excited states of the exciton in a 2D semiconductor with anisotropic effective masses of electrons and holes. The electron–hole interaction is described by the Rytova–Keldysh potential, which is considered beyond the standard zero-thickness approximation. The exciton binding energies calculated for BP and TMD (molybdenum disulphide and tungsten disulphide) monolayers are compared with previously published data.

Fluorescence of the modified GFP chromophore diethyl-ABDI-BF2 dispersed in PMMA matrix is studied on top of glass, continuous and perforated optically thin silver films. In polymer, the fluorescence decay kinetics becomes non-exponential and can be described by the distribution of rate constants. The results demonstrate shortening of the excited state lifetime in the presence of silver and broadening of the lifetime distribution caused by the nanoholes.

Dynamic deuterium (D) retention properties of tungsten (W) are investigated under steady-state D plasma exposure in the PISCES-A linear plasma device. In contrast to static retention, dynamic retention is quickly released from the material at the termination of the incident plasma flux, and thus in-operando laser-induced breakdown spectroscopy (LIBS) measurements have been conducted during steady-state D plasma exposure. A procedure is, first, established to extract the dynamic retention component from the in-operando LIBS D I 656.1 nm line intensity, which can contain contributions from dynamic and static retention as well as background D/D2 gas, excited by both steady-state and laser-induced plasmas. Using the developed procedure, the dynamic D retention in W is systematically examined while scanning the following plasma exposure parameters: incident ion energy, Ei, sample temperature, Ts, incident ion flux, Γi. No clear Ei dependence is seen in the range of Ei ~ 45-175 eV, as expected from a small variation in the average implantation depth (~3-6 nm) of D in W. The dynamic retention is found to monotonously decrease with increasing Ts from 348 to 573 K, while the total static retention is reported to peak at Ts ~ 500-600 K. It is revealed that the dynamic retention linearly increases with increasing Γi, and then saturates at Γi ≥ 0.75 × 1021 m-2s-1. Possible physical mechanisms for the observed dependence of the dynamic retention on Ts and Γi are discussed. Furthermore, sequential pure He, followed by pure D, plasma exposures show that the dynamic D retention is not strongly affected by He bubbles in the near-surface region.

The capacitive argon discharge operated in the intermediate pressure regime is studied by performing one-dimensional particle-in-cell Monte Carlo collision simulations. First, the basic object-oriented plasma device code (oopd1-v1) is strictly benchmarked against the well-established xpdp1 code over a wide range of pressure (0.05 – 15 Torr) and varying blocking capacitor of the external circuit (5 – 10^5nF), and excellent agreement is obtained. The oopd1-v1 is upgraded to v2 and v3, by adding excited atoms modeled as time- and space-evolving fluid species. The metastable Arm, the radiative Arr, and the Ar(4p) manifold, and their roles in discharge equilibrium are explored. It is found that the presence of the metastable Arm enhances the plasma density by a factor of 3 at 1.6 Torr and even higher at pressures up to 5 Torr. At low pressure (0.05 Torr), electron impact ionization from the ground state atom dominates the ionization over the whole discharge region, while metastable pooling and step-wise ionization has small contribution. The proportion of metastable pooling ionization and step-wise ionization increases with increasing pressure and becomes the dominant ionization source at 5 – 15 Torr.

Based on the measured absorption coefficient for the atomic iodine transition in the mixtures of iodides with helium we have determined the fractions of the excited atomic iodine produced by dissociation of CH3I, CF3I, i-C3F7I, C2F5I and C2H5I molecules in a self-sustained pulsed discharge. In the 1: (3 – 15) mixtures of iodides with helium at the pressure 133 – 400 Pa these fractions amount to 0.29 for CF3I and CH3I, 0.2 for i-C3F7I, and 0.31 for C2F5I and C2H5I. The accuracy of determining the excited iodine fraction is 10%. The numerical modelling is carried out for the mixtures containing CF3I. The calculated values of the excited iodine fraction for the mixture with CF3I agree well with the experimental data.

The orientation switching of a single azobenzene molecule on Au(111) surface excited by tunneling electrons and/or photons has been demonstrated in recent experiments. Here we investigate the rotation behavior of this molecular rotor by first-principles density functional theory (DFT) calculation. The anchor phenyl ring prefers adsorption on top of the fcc hollow site, simulated by a benzene molecule on close packed atomic surface. The adsorption energy for an azobenzene molecule on Au(111) surface is calculated to be about 1.76 eV. The rotational energy profile has been mapped with one of the phenyl rings pivots around the fcc hollow site, illustrating a potential barrier about 50 meV. The results are consistent with experimental observations and valuable for exploring a broad spectrum of molecules on this noble metal surface.

Computational fluid dynamics plasma simulations of a capillary capacitively coupled radio frequency thruster (C3RFT) discharge with front powered electrode was performed. Good agreement with experimental results was obtained for the global parameters of the thruster. The spatial characteristics of the discharge were analyzed. DC bias is found to develop in accordance with classical theory of asymmetric capacitive discharge. The electrons temperature in the plasma bulk is ~ 2 eV and increasing the sheath near the powered electrode to ~ 6 eV. The plasma density is 1019 m-3 whereas excited argon species are 1020 m-3. The thrust can be completely attributed to gas dynamic acceleration.

We present a predictable single-photon source (SPS) based on a silicon vacancy centre in nanodiamond which is optically excited by a pulsed laser. At an excitation rate of 70 MHz the source delivers a photon flux large enough to be measured by a low optical flux detector (LOFD). The directly measured photon flux constitutes an absolute reference. By changing the repetition rate of the pulsed laser, we are able to change the photon flux of our SPS in a controllable way which in turn can act as a reference. The advantage of our method is that it does not require precise knowledge of the source efficiency, but the source is calibrated by the LOFD and can be used for detector responsivity characterizations at the few-photon level.

An experimental setup of laser-induced graphite plasma was built and the spectral characteristics and properties of graphite plasma were studied. From the temporal behavior of graphite plasma, the duration of CN partials (B2 Σ+ → X2 Σ+) emission was two times longer than that of atomic carbon, and all intensities reached the maximum during the early stage from 0.2 μs to 0.8 μs. The electron temperature decreased from 11807 K to 8755 K, the vibration temperature decreased from 8973 K to 6472 K, and the rotational temperature decreased from 7288 K to 4491 K with the delay time, respectively. The effect of the laser energy was also studied, and it was found that the thresholds and spectral characteristics of CN molecular and C atomic spectroscopy presented great differences. At lower laser energies, the electron excited temperature, the electron density, the vibrational temperature and rotational temperature of CN partials increased rapidly. At higher laser energies, the increasing of electron excited temperature and electron density slow down, and the vibrational temperature and rotational temperature even trend to saturation due to plasma shielding and dissociation of CN molecules. The relationship among the three kinds of temperatures was Telec>Tvib>Trot at the same time. The electron density of the graphite plasma was in the order of 1017 cm−3 and 1018 cm−3.

1,1,2-trichloroethane is transformed by the action of low-voltage (60 V DC) pulse discharge in the liquid medium in the nanostructure, cis-ClCH = CHCl, trans-ClCH = CHCl, CH2 = CCl2 and HCl. Conversion 1,1,2-trichloroethane 21 wt%, hydrogen chloride yield was 88.4 wt%, yield solid phase 11.6 wt%. The morphology and composition of solid phase products have been determined. According to energy dispersive X-ray spectroscopy, solid-phase products have an elemental composition, % atom: carbon — 90.5-94.2, chlorine — 1.35.4, oxygen — 3.1-4.5. The structures of 1,1-dichloroethylene and cis-, trans-1,2-dichloroethylene, as well as the isomer ratios were determined by 1H NMR. The relative content of isomers: cis-1,2-dichlorethylene 44%, trans-1,2-dichlorethylene 34%, 1,1-dichloroethylene 22%. Quantum-chemical modeling revealed the mechanism of formation of the obtained dichlorethylenes. According to the calculation results, 1,1,2-TCA is involved in the reaction in the triplet state. The difference in energy between the ground and excited states is 66.2 kcal/mol. The elimination of HCl is carried out by an activated chlorine atom generated during the transfer of 1,1,2-TCA under the action of electric discharges from the singlet state to the triplet state.

The dynamic motion of DNA oligomers at the nanoscale gap between nanoelectrodes is measured under plasmonic excitation using laser irradiation. The use of a nanogap enables highly sensitive detection of individual molecules using an electrical readout or an optical readout such as Raman spectroscopy. However, the target molecule must reach the nanogap in order to be detected. This study focuses on the use of plasmonic excitation to trap molecules at the nanogap surface. The nanogap electrode is fabricated by electromigration and is, therefore, a much smaller nanogap than the top-down fabrication in the conventional plasmonic trapping studies. To demonstrate the individual molecule detection and to investigate the molecular behavior, the molecules are monitored using an electrical readout under a bias voltage instead of an optical readout used in the conventional studies. The conductance change due to DNA oligomer penetration to the nanogap is observed with the irradiated light intensity of over 1.23 mW. The single-molecule detection is confirmed irradiating the laser to the nanogap. The results suggest that DNA oligomers are spontaneously attracted and concentrated to the nanogap corresponding to the detection point, resulting in high detection probability and sensitivity.

Novel measurements of the neutron energy spectra of the 9Be(d,n)10B reaction with a thick beryllium target are performed using a fast neutron time-of-flight (TOF) spectrometer for the neutron emission angles and , and the incident deuteron energies are 250 and 300 keV, respectively. The neutron contributions from the 9Be(d,n)10B reaction are distributed relatively independently for the ground state and the first, second, and third excited states of 10B. The branching ratios of the 9Be(d,n)10B reaction for the different excited states of 10B are obtained for the neutron emission angles and , and the incident deuteron energies are 250 and 300 keV, respectively. The branching ratio of the 9Be(d,n)10B reaction for the third excited state decreases with increase in the incident deuteron energy, and the branching ratios for the ground state and the second excited state increase with increase in the neutron emission angle.

The electron temperature T e and density N e of atmospheric-pressure non-equilibrium dielectric barrier discharge argon (Ar) plasma are measured with optical emission spectroscopy. Continuum emission due to bremsstrahlung is applied to the analysis of the electron temperature and density with the spectrometric system in the visible wavelength range calibrated absolutely. The assumption of the Maxwellian electron energy distribution function (EEDF) results in T e ≃ 0.29 eV and N e ≃ 1.1 × 1016 cm−3, whereas the Druyvesteyn EEDF leads to the result T e ≃ 0.79 eV and N e ≃ 1.4 × 1014 cm−3. To confirm the validity of these values, several line intensities of the excited states of the Ar atom are observed experimentally and compared with the theoretical population densities calculated by the Ar collisional–radiative (CR) model that includes atomic collisional processes. It is confirmed that the order of the observed excited-state number densities agrees well with that calculated numerically by the CR model with the Druyvesteyn EEDF, while the Maxwellian EEDF gives poor results.

Lifetimes of excited states in the Kπ = 0− octupole band and γ-vibrational of 228Th have been measured using the fast timing setup at the University of the West of Scotland (UWS). The setup consists of two cerium doped LaBr3 fast scintillators placed equidistant from the radioactive source 232Th. The states of interest have been analysed by doing the triple γ – γ – time coincidence analysis and using the fast-timing technique, mirror-symmetric centroid difference method. Octupole collectivity in 228Th nucleus is also investigated by calculating the enhanced electric dipole moments and transition rates in excited states followed by lifetime measurements in octupole band.

Long-lived metastable states in neutral tungsten are shown to potentially impact measurements of tungsten erosion from plasma facing components. Time-dependent collisional radiative modeling of neutral tungsten is used to analyze the role of these states in tungsten emission and ionization. The large number of non-quasistatic atomic states in neutral tungsten can take on the order of milliseconds to reach equilibrium, depending on plasma conditions, causing erosion measurements to be affected by the metastable populations. Previous measurements using the 400.88 nm tungsten emission line could be affected by these non-quasistatic metastable effects. Therefore, a scheme for measuring the relative metastable fractions is proposed through simultaneous observation of multiple ultraviolet spectral lines of neutral W. The accuracy of gross erosion measurements could potentially be increased by inclusion of these previously unconsidered metastable effects.

We consider diode-pumped alkali vapour lasers (DPALs), which make it possible to achieve a high output power. Characteristics of such DPALs strongly depend on the physical properties of buffer gases and on structural parameters of a vapour cell. Special attention is paid to a diode-pumped rubidium vapour laser (DPRVL): We have investigated the effect of different conditions on its characteristics. The results show that the linewidth of the D2 line of a DPRVL and the fine-structure mixing rate between two excited energy levels, which are two crucial factors in implementing a high-power DPRVL, increase with the pressure of buffer gases and the temperature of the vapour cell. It is demonstrated that the population ratio of two excited energy levels is close to that corresponding to a thermal equilibrium as the pressure of buffer gases and the temperature of the vapour cell become higher. We have found that the optimal values of the methane pressure, the cell temperature and the cell length can be determined through a kinetic analysis. The conclusions can be valuable for designing configurations of an end-pumped DPAL.

The experimental results on the dissociation of iodine molecules in the presence of single oxygen molecules under a widerange variation of the oxygen–iodine composition are presented. The rate constants are determined as 4.3 × 10-17 cm3 s-1 for the reaction O2(1Δ) + O2(1Δ) → O2(1Σ) + O2(3Σ) (reaction 1), 2.8 × 10-13 cm3 s-1 for the reaction O2(1Δ) + I(2P1/2) → O2(1Σ) + I(2P3/2) (4) and 8.3 × 10-11 cm3 s-1 for the reaction O2(1Σ) + I2 → O2(3Σ) + 2I (2). The analysis of the experimental results shows that for different compositions of the active medium of the oxygen–iodine laser the iodine dissociation occurs via the chain of reactions 1, 2, O2(1Δ) + I(2P3/2) → O2(3Σ) + I(2P1/2), 4 and in the cascade process I2 + I(2P1/2) → I2(u) + I(2P3/2), I2(u) + O2(1Δ) → 2I + O2(3Σ). For typical active medium compositions of the supersonic chemical oxygen–iodine laser, the contributions of each of the mechanisms to the dissociation are comparable. The experiments carried out did not reveal any contribution from the vibrationally excited oxygen molecules to the iodine dissociation. Thus, the performed experiments and the conclusions drawn from them completely confirm the mechanism of iodine dissociation, proposed earlier.

Observations are presented of the phenomenon of the enhancement in electron density and temperature that is caused by a powerful pump wave at a frequency near the fifth gyrofrequency. The observations show that the apparent enhancement in electron density extending over a wide altitude range and the enhancement in electron temperature around the reflection altitude occur as a function of pump frequency. Additionally, the plasma line spectra show unusual behavior as a function of pump frequency. In conclusion, the upper hybrid wave resonance excited by the pump wave plays a dominating role and leads to the enhancement in electron temperature at the upper hybrid altitude. The phenomenon of apparent enhancement in electron density does not correspond to the true enhancement in electron density, this may be due to some mechanism that preferentially involves the plasma transport process and leads to the strong backscatter of radar wave along the magnetic line, which remains to be determined.

Atmospheric pressure discharges excited by repetitive nanosecond pulses have attracted significant attention for various applications. In this paper, a plate-plate discharge with airflows is excited by a repetitive nanosecond pulse generator. Under different experiment conditions, the applied voltages, discharge currents, and discharge images are recorded. The plasma images presented here indicate that the volume discharge modes vary with airflow speeds, and a diffuse and homogeneous volume discharge occurs at the speed of more than 35 m/s. The role of airflows provides different effects on the 2-stage pulse discharges. The 1st pulse currents nearly maintain consistency for different airflow speeds. However, the 2nd pulse current has a change trend of first decreasing and then rapidly increasing, and the value difference for 2nd pulse currents is about 20 A under different airflows. In addition, the experimental results are discussed according to the electrical parameters and discharge images.

We present precise measurements of polarizabilities of cesium nS1/2 (n = 65–75) Rydberg states by Stark spectroscopies. In experiment, Rydberg atoms are excited via a two-photon scheme of a standard magneto-optical trap and detected by the field ionization technique. The Stark shift is measured by analysing the spectroscopy under an external electric field. The polarizability, α, is acquired by fitting the experimental data of Stark shifts with Δ W = − 1 2 α E 2 . The theoretical model is applied to numerically simulate the Stark map and corresponding level shifts, related deviation between the experimental measurements and calculations are less than 2%. The scaling law of polarizabilities, A ⋅ ( n * ) 7 + B ⋅ ( n * ) 6 (n* is effective principal quantum number), is attained, that shows a good agreement with the measurements.

A scheme of plasma–chemical mid-IR hydrogen fluoride (HF) lasing is proposed, in which electrons of femtosecond filament are produced in argon and give rise to a chain of plasma–chemical reactions occurring with SF6 and H2 added to the argon bath and resulting in the formation of vibrationally excited HF molecules. The conditions for the occurrence of amplified spontaneous emission and lasing in the range of 2.7–3 μm in a selected gas mixture at a total pressure of several atmospheres can be realized under the action of a femtosecond laser on Cr-forsterite with a wavelength of 1.24 μm. In numerical experiments, it was demonstrated that HF lasing energy at the level of 1.5 μJ are achievable for typical monofilament plasma parameters.

Electron affinities (EA) of most lanthanide elements still remain unknown owing to their relatively lower EA values and the fairly complicated electronic structures. In the present work, we report the high-resolution photoelectron spectra of atomic cerium anion Ce− using the slow electron velocity-map imaging method in combination with a cold ion trap. The electron affinity of Ce is determined to be 4840.62(21) cm−1 or 0.600160(26) eV. Moreover, several excited states of Ce− (4H9/2, 4I9/2, 2H9/2, 2G9/2, 2G7/2, 4H13/2, 2F5/2, and 4I13/2) are observed.

We have investigated the electronic properties of fluoromethane compounds to examine the electronic properties and the primary dissociation channels from a point of view of computational chemistry. For electron attachment process, it is very important to represent the observed negative mass spectrum as a function of electron energy that the calculation of MP2 method for negative ion and the subsequent calculation of EOMCCSD method to estimated the first excited state of the negative ion. In the case of evaluation of dissociated fragments through excitation process, it is very important that the structure change of the excited fragment (from pyramidal to planar) is taken into account. Evaluation of Jahn-Teller distortion for highly symmetrical CHF3 and CH3F is also very important to estimate the fragmentation process through the excitation.The calculated results after these treatments give the satisfactorily representation to the experimental values and moreover some prediction to experimentally unknown values.

An all-optical, near-resonant laser atom trap is used to prepare an electronically excited and polarized gas target at mK-temperature for complete photo-ionization studies. As a proof-of-principal experiment, lithium atoms in the 2$^2$P$_{3/2}$($m_l$=+1) state are ionized by a 266 nm laser source, and emitted electrons and Li$^+$ ions are momentum analyzed in a COLTRIMS spectrometer. The excellent resolution achieved in the present experiment allows not only to extract the relative phase and amplitude of all partial waves contributing to the final state, it also enables to characterize the experiment regarding target and spectrometer properties. Photo-electron angular distributions are measured for five different laser polarizations and described in a one-electron approximation with excellent agreement.

The interaction between single Tm2O3 layers in electroluminescent Al2O3/Tm2O3 nanolaminate films fabricated by atomic layer deposition, is investigated through the adjustment of the Al2O3 spacer layer thickness and annealing temperature. The EL intensities and decay time from different energy levels of the Tm3+ ions in Al2O3/Tm2O3 nanolaminates are explored, all of which derive a ~1.5 nm Forster distance, manifesting a critical distance of ~3 nm to eliminate the non-radiative interaction between adjacent Tm2O3 layers, which quenches the excited electrons to the ground energy level rather than relax to lower excited states. The diffusion of Tm3+ ions and resulting cluster formation under high temperature annealing also influence the abovementioned interaction, and 800 °C is suitable to minimize the diffusion while activate Tm3+ emissions. This work provides the basis for the exploitation of rare earth-doped nanolaminates in optical communication and silicon-based optoelectronics.

International audience; We present a spectroscopy scheme for the 7-kHz-wide 689-nm intercombination line of strontium. We rely on shelving detection, where electrons are first excited to a metastable state by the spec-troscopy laser before their state is probed using the broad transition at 461 nm. As in the similar setting of calcium beam clocks, this enhances dramatically the signal strength as compared to direct saturated fluorescence or absorption spectroscopy of the narrow line. We implement shelving spectroscopy both in directed atomic beams and hot vapor cells with isotropic atomic velocities. We measure a fractional frequency instability ∼ 2 × 10 −12 at 1 s limited by technical noise-about one order of magnitude above shot noise limitations for our experimental parameters. Our work illustrates the robustness and flexibility of a scheme that can be very easily implemented in the reference cells or ovens of most existing strontium experiments, and may find applications for low-complexity clocks.

Excitation wavelength dependence of red persistent luminescence in CaS:Eu2+,Tm3+ phosphor is reported. Persistent luminescence appears under visible light excitation in the wavelength region of 400–600nm. Photon energy from white light-emitting diode lamps is possibly stored in this material. This sulfide phosphor is synthesized using iodine vapor. Under iodine vapor, Eu2+ and Tm3+ are found to be efficiently included in CaS. The concentration dependence of Eu2+ is studied, and the optimum concentration is 0.05%. Trap depth of 0.27–0.33eV contributing to persistent luminescence is evaluated by using thermoluminescence.

A quick method is proposed for measurement of the carbon-related hole trap (H1: +0.87 eV) density in an n-type GaN homoepitaxial layer using dual-color-sub-bandgap-light-excited isothermal capacitance transient spectroscopy. Shorter wavelength (390 nm) light irradiation is employed to cause the hole traps to be in the hole-occupied state. Longer wavelength (660 nm) light irradiation is then used to emit the hole from the trap to the valence band. The photoemission of holes is much quicker than the thermal emission, which reduces the measurement time. The trap density can be calculated from the capacitance transient.

By combining time-dependent density functional tight binding (TD-DFTB) calculations for electrons with molecular dynamics simulations, time evolution of excited state relaxation and single electron self-trapping of silicon nanosheets (SinHm) are investigated. We identify the atoms and bonds contributing to the excitations and observe the time evolution of charge density, indicating the migration of exciton from initial position to neighboring bonds. Different temperature 50K and 100K are attempted in the MD simulations, and the temperature is found to affect the electronic localization. Our simulations reveal the formation of exciton trapping and localization on certain bonds upon excitation within the timescale about 200-300fs. In summary, TD-DFTB excited state MD simulations can provide interesting insights into photoreactions and have crucial implications in modulating the exciton transport efficiency in strongly confined low-dimensional systems.

This paper describes the results of modeling of a dielectric barrier discharge (DBD). Filamentary structure of DBD is taken into account in the model by introducing the ratio of the cross section area of a microdischarge to the electrode area as a parameter of the model. Discharge and afterglow stages in the gas flow were studied using a zero-dimensional model for a DBD microdischarge channel. The results of modeling are compared with literature data for [O] number densities in a single pulse nanosecond discharge, and with our own measurements of ozone formation in the DBD. Measurements of ozone number density in oxygen and in mixtures of oxygen with methane served as means of validating the DBD model. The best agreement of the calculated and experimental dependences of [O3] number densities on the discharge energy load was observed, when processes involving vibrationally excited ozone were accounted for together with the discharge microstructure.

Synopsis Results from the first soft X-ray user experiment at the European XFEL on nonlinear photon-matter interaction will be presented. Angle-resolved electron time-of-flight spectroscopy employed at the AQS (Atom-ic-like Quantum Systems) endstation of the SQS (Small Quantum Systems) instrument reveals insight into the character of resonances in highly transient, core ionized neon ions, i.e. Ne+ 1s12s22p6 → Ne+* 1s02s22p6np, together with their respective relaxation dynamics. Enabled by the unique properties of the European XFEL, novel perspectives on efficient nonlinear spectroscopy will be discussed.

Synopsis The semiclassical two-centre convergent close-coupling approach is applied to study total ionisation, Balmer emission as well as various excitation and electron-capture transitions in proton collisions with the ground and n = 2 states of atomic hydrogen, where n is the principal quantum number. The results for polarisation fraction of the Balmer-α emission induced in p-H(1s) collisions are in good agreement with experiment at intermediate energies, but surprisingly not at higher energies.

Synopsis We present work on the disentanglement of core dynamics and binding potential influences for Above-Threshold Ionisation in Helium prepared in an excited p state, interacting with a mid-IR field. This was formed by comparing the Coulomb Quantum-Orbit Strong-Field Approximation (CQSFA) with B-spline Algebraic Diagrammatic Construction (ADC) simulations. This may lead to the identification of initial momentum distributions, for tunneling and re-scattering instances, from the CQSFA perspective. The latter method is an inverse approach; thus, the ADC simulations will allow comparison of findings.

Synopsis Study of electron-impact excitation of few highly charged tungsten ions viz. Tm-, Er- and Ho-like has been done using relativistic distorted wave theory (RDW). The dipole allowed transitions of these ions are considered and electron-impact excitation cross section are reported in the wide range of energy. These calculated cross section are also fitted with suitable analytical expressions for the direct use in plasma modelling. Further-more, the polarization of the emitted photons on consequent decay of the excited tungsten ions are calculated by utilizing density matrix theory.

Synopsis The photoexcitation rate for ultralong-range Rydberg molecules is sensitive to the initial spatial sepa-ration of the atoms from which they are formed. Here we explore the photoexcitation of different molecular vibrational states as a probe of spatial correlations in a cold atomic gas.

Synopsis We found that the XUV excited caffeine undergoes nondadabatic cascade via more than 100 shake-up states within the time constant of 40 fs by using femtosecond XUV-NIR pump-probe photo-ion spectroscopy and the SAC-CI level of ab-initio many-body theory. This nonadiabatic cascade results in the photofragmentation to specific large fragments. Furether ionization by NIR probe during the cascade increases the small fragments CH3 +, CO+ etc. This results show that both vibronic coupling and electron correlation are the keys for the femtochemistry in the highly-correlated electronic excited states.

Tandem mass spectroscopy ($\textrm{MS}^2$) combined with single photon excitation in the VUV range (photon energy 4.5-9 eV) was performed on protonated uracil ($\textrm{UraH}^{+}$) and uridine ($\textrm{UrdH}^{+}$). The precursor ions with $m/z\;113$ and $m/z\;245$ respectively were produced by an Electrospray Ionization source (ESI) and accumulated inside a quadrupole ion trap mass spectrometer. After irradiation with tunable synchrotron radiation, product ion mass spectra were obtained. Fragment yields as a function of exciting energy show several maxima that can be attributed to the photo-excitation into different electronic states. For uracil, vertically excited states were calculated using the equation-of-motion coupled cluster approach (EOM-CCSD) and compared to the observed maxima. This allows to establish correlations between electronic states and resulting fragment masses and can thus help to disentangle the complex deexcitation and fragmentation pathways of nucleic acid building blocks above the first electronically excited state. Photofragmentation of the nucleoside uridine shows a significantly lower variety of fragments, indicating stabilization of the nucleobase by the attached sugar., author version

The decolorization of the indigo carmine solution was performed by argon dielectric barrier discharge (DBD) excited on a target solution and the effect of the gap distance on the water treatment characteristics were investigated for the gap distance between 1.0 and 2.5 mm. The argon DBD was excited by the 3-kHz sinusoidal voltage with the fixed discharge power between 1.72 and 1.76 W for any gap distance. Voltage and current waveforms and Lissajous figures were acquired to investigate the electrical characteristics of the DBD. Compared with fixing the discharge energy, the higher decolorization rate was obtained with the shorter gap distance. Therefore, shortening gap distance could lead to increased decolorization efficiency of the indigo carmine solution. The mechanism of the higher efficiency with the shorter gap distance was discussed on the basis of the electrical characteristics and possible plasma chemical reactions in the argon DBD on the solution surface.

A composite mechanoluminescent layer has been produced on the surface of polymethylmethacrylate by liquid-phase embedding of SrAl2O4:(Eu2+, Dy3+) phosphor microparticles into the polymethylmethacrylate surface layer. The photoluminescence and mechanoluminescence of the obtained layer have been investigated. The mechanoluminescence was excited by the short acoustic pulses. A possible mechanism of mechanoluminescence excitation is under discussion. The produced composite layer is shown to exhibit high efficiency of “mechano-optical” transformation.

The paper presents the results of experimental measurements of the emission properties of water plasma in an inductive discharge. The power of the inductive discharge was 600 W at a frequency of 27 MHz and a pressure from 0.25 to 4 mbar. Plasma temperature was estimated from the Balmer hydrogen series using relative intensities method. It is shown that in this pressure range, the plasma is not in equilibrium and the energy difference between individual excited states increased with distance from the tube axis. The plasma heating time was estimated from the dynamics of the spectral line intensities to be 200 ms.