Stark Splitting Research Articles

Spectroscopic diagnostics and electric field measurements in the near-cathode region of an atmospheric pressure microplasma jet

Linear Stark splitting of the H $_{\beta}$ Balmer line components and spatially resolved optical emission spectroscopy (OES) measurements were used to estimate the electric field gradient in the cathode sheath region (~70 μm long) of an atmospheric pressure direct current argon flow-stabilized microplasma jet. Also, plasma parameters in the negative glow region were investigated by both OES and electrical diagnostics. The microplasma jet was operated for current ranging from 10 to 110 mA. OH (A 2 ${\rm\Sigma}^+$ , v = 0 $\to$ X 2 ${\rm\Pi}$ , v’ = 0) rotational bands at 306.357 nm and also the Ar 603.213 nm line were used to determine the gas temperature, which ranges from 600 to 1000 K. Electron number density, ranging from 4.1 × 1014 to 8.5 × 1014 cm-3, was determined through analysis of the H $_{\beta}$ line. Electron excitation temperature was also measured from the ratio of two Mo lines (8500–18 000 K) and from Boltzmann-plot of Ar 4p–4s and 5p–4s transitions (11 000–13 500 K).

Photoluminescence in electronic ferroelectric Er1−xYbxFe2O4

Strong Stark splitting, which is nearly independent of the R-ions replacement, has been observed through the photoluminescence investigation of electronic ferroelectric Er1−xYbxFe2O4 (x=0, 0.8, 0.9, and 0.95). Initially multiple radiative decay channels have been investigated, especially the visible transition F49/2→I415/2, of which a quenching effect has been observed. A series of small non-Raman peaks have been observed superimposed on a broadband photoluminescence spectrum, of which we tentatively assign Stark splitting to be the cause. The splitting of the F49/2 and I415/2 levels is found to be 54 meV and 66 meV, respectively. This unusually large Stark splitting at visible range indicates the existence of strong local field originated from the W-layer in the charge-frustrated ErFe2O4.

Measurements of the internal magnetic field using the B-Stark motional Stark effect diagnostic on DIII-D (invited)

Results are presented from the B-Stark diagnostic installed on the DIII-D tokamak. This diagnostic provides measurements of the magnitude and direction of the internal magnetic field. The B-Stark system is a version of a motional Stark effect (MSE) diagnostic based on the relative line intensities and spacing of the Stark split D(α) emission from injected neutral beams. This technique may have advantages over MSE polarimetry based diagnostics in future devices, such as the ITER. The B-Stark diagnostic technique and calibration procedures are discussed. The system is shown to provide accurate measurements of B(θ)/B(T) and ∣B∣ over a range of plasma conditions. Measurements have been made with toroidal fields in the range of 1.2-2.1 T, plasma currents in the range 0.5-2.0 MA, densities between 1.7 and 9.0×10(19) m(-3), and neutral beam voltages between 50 and 81 keV. The viewing direction and polarization dependent transmission properties of the collection optics are found using an in situ beam into gas calibration. These results are compared to values found from plasma equilibrium reconstructions and the MSE polarimetry system on DIII-D.

Grating spectrometer system for beam emission spectroscopy diagnostics using high-energy negative-ion-based neutral beam injection on LHD

A beam emission spectroscopy (BES) system was developed for density gradient and fluctuation diagnostics in the Large Helical Device (LHD). In order to cover the large Doppler shift of the Hα beam emission because of the high-energy negative-ion-based neutral beam atom (acceleration voltage V(acc)=90-170 kV) and the large motional Stark splitting due to the large v×B field (magnetic field B=3.0 T), a grating spectrometer was used instead of a conventional interference filter system. The reciprocal linear dispersion is about 2 nm/mm, which is sufficient to cover the motional Stark effect spectra using an optical fiber with a diameter of 1 mm.

SEM-mapped micro-photoluminescence studies of highly luminescent micro-clusters in erbium-doped silicon-rich silicon oxide

Abstract This paper reports on the formation of unique micrometer-scale clusters in erbium-doped silicon-rich silicon oxide (ErSRSO) thin films produced by thermal evaporation. Through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), we identify these micro-clusters as structures where the film curves away from the substrate to encase erbium-rich aggregates. Even though erbium aggregation has been reported to cause quenching, we demonstrate that the micro-clusters as a whole can exhibit significantly enhanced erbium photoluminescence (PL), with emissions over 24 times brighter than the surrounding non-cluster region. Mapping micro-photoluminescence measurements onto SEM images reveals that the erbium aggregates alone do not generate the enhanced PL, but rather the thin film encasing the aggregates is the origin of the emissions. Analysis of the PL Stark splitting shows a correlation between the micro-clusters’ fine structure and the strength of their PL. Taken together, the above evidence indicates that the micro-clusters’ strong PL is produced by changes in the local environment of the Er 3+ inside the thin film surrounding the erbium-rich aggregates.

High-Frequency Einstein–Podolsky–Rosen Entanglement via Atomic Memory Effects in Four-Wave Mixing

Atomic memory effects occur when the atomic relaxation times are comparable to or much longer than the cavity relaxation times. We show that by using the memory effects, it is possible to obtain high-frequency Einstein–Podolsky–Rosen entanglement between a pair of Stokes and anti-Stokes fields in a four-wave mixing system. The physical origin is traced to the dynamical Stark splittings of dressed states due to the parametrically amplified fields. This mechanism provides an alternative and efficient way for sideband entanglement.

ChemInform Abstract: Observation of Dynamic Stark Splitting in Infrared-Infrared Double Resonance in Methyl Fluoride.

Abstract Dynamic Stark splitting has been observed by scanning the Q P (5, 3) transition in the 2 ν 3 - ν 3 band in 13 CH 3 F with a CO 2 -laser based infrared microwave sideband generator while pumping the Q R (4, 3) transition in the ν 3 band with a second CO 2 laser. Similar splitting has been observed in the Q Q (12, 9) and Q R (12, 9) transitions in the 2 ν 3 - ν 3 band of 12 CH 3 F while pumping the Q R (11, 9) transition in the ν 3 band. The lineshapes of these and other double resonance effects have been fit to high accuracy by means of a computer program that computes the spectrum by solving the density matrix equations for a three-level system including summation over the spatially degenerate states and numerical integration over the velocity. The effects of contributions from collisional energy transfer, frequency modulation of the lasers, and misalignment of the laser beams have been calculated and are discussed. Difficulties that must be overcome in order to use these experiments for determination of energy transfer rates are described.

Characterization of hollow cathode fall field strength measured by Doppler-free two-photon optogalvanic spectroscopy via Stark splitting of the 2S level of hydrogen and deuterium

Doppler-free two-photon optogalvanic spectroscopy has been applied to measure the strong electric field strength and the cathode fall characteristics of hollow cathode discharges operated in hydrogen and deuterium via the Stark splitting of the 2S level of atomic hydrogen isotopes. In this paper we show similarities and differences in the tendencies of the cathode fall characteristics of hydrogen and deuterium in a wide range of identical discharge parameters.

Optical spectroscopy investigation on distribution of Eu3+ in nanostructured glass ceramics

The time-resolved luminescence spectra of the Eu3+ doped SiO2–Al2O3–NaF–YF3–EuF3 precursor glass reveal that Eu3+ ions locate in both the oxygen-coordination environment and the fluorine-coordination one. After crystallization induced by heat treatment, the orthorhombic YF3 nanocrystals with mean size of 22 nm embedded homogeneously in the glassy matrix. The Stark splitting emission, the low electric dipole D50→F72 transition, the disappearance of the O2−–Eu3+ charge transfer band and the reduction in Ω2 value indicate the partition of Eu3+ into the YF3 lattice. Moreover, the nearly single-exponential luminescence decay curves of the Eu3+:D50 and D51 levels for the 0.1% Eu3+ doped glass ceramic evidence that Eu3+ ions mainly occupy the Y3+ sites.

Local order effects on the photoluminescence of Er 3+ in a novel vitreous matrix of the CdO–ZnO–V 2O 5 system and manifolds in Zn xAl 2−xO 3 micro crystalline aggregates

The ion Er 3+ was introduced into a new kind of glassy matrices prepared from a mixture of CdO–ZnO–V 2O 5 and Er(NO 3) 3·5H 2O as source of Er 3+ ions. The obtained glasses were characterized by infrared spectroscopy and micro photoluminescence and micro Raman spectroscopies. The glass formation process produced Al diffusion from the crucible to the oxides mixture yielding crystalline micro aggregates. The room temperature photoluminescence spectra showed transitions from different Er 3+ levels in the 450–900 nm range. In particular, the 4F 9/2 → 4I 15/2 transitions were strongly affected by local electric fields since these transitions presented Stark effect splittings whose intensity was dependent on the atomic order surrounding the Er 3+ ions. It was found that a highly reproducible multiplet emission was particularly strong in crystalline micro-regions of Zn x Al 2− x O 3 immersed in the vitreous matrix.

Up-conversion photoluminescence characteristics of Yb3+:Er3+:Tm3+ co-doped borosilicate glasses

Yb3+:Er3+:Tm3+co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb3+, Er3+ and Tm3+ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power. The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.

Spin edge states in two-dimensional electron systems

We consider the spin edge states, induced by the combined effect of spin-orbit interaction and hard-wall confining potential, in a two-dimensional electron system exposed to a perpendicular quantizing magnetic field. We derive an exact analytical formula for the dispersion relations of spin edge states and analyze their energy spectrum, velocity, and average transverse position. It is shown that by removing the spin degeneracy, spin-orbit interaction splits the spin edge states not only in the energy but also induces their spatial separation. It is revealed that at low magnetic fields, due to the Stark splitting of the spin-resolved edge states, the high-energy bands exhibit anti-crossings. This results in an additional structure in the behavior of the velocity of current-carrying edge states.

Evolution and Eu3+ Doping of Sol−Gel Derived Ternary ZnxTiyOz - Nanocrystals

Alloyed ZnxTiyOz nanostructures were prepared by a thermal condensation process employing ethanolic mixtures of zinc acetate dihydrate and titanium alkoxide, without additional use of additives. It has been found that the nanocrystal growth takes place at temperatures above 350 °C yielding cubic spinel Zn2TiO4, cubic ZnTiO3, or hexagonal ilmenite ZnTiO3. Their preferential appearance and size tuning between 5 and 80 nm was possible by varying the starting sol condensation conditions, Zn/Ti-ratio and sintering temperature. The electronic transitions in these ternary oxide semiconductor nanocrystals were observed at photon energies between 3.6 and 3.8 eV that reflects the presence of a wider optical gap than that known for the corresponding binary oxides ZnO and TiO2. We also noticed a strong influence of Eu3+ doping on the resulting structural and optical properties. Despite its large ionic size, this lanthanide efficiently intervenes in the evolution process by blocking the nanocrystal growth and the cubic-to-hexagonal transformation in ZnTiO3. Its preferential incorporation into spinel phase is manifested by the activation of a strong red intrashell fluorescence and a significant Stark splitting of the 5FJ states. The comparison of the spectral response and asymmetry ratio values deduced from the experimental Eu3+ luminescence data collected on structurally similar Zn2TiO4 and ZnTiO3 nanophases suggests the hypothesis that cubic ZnTiO3 has a structure of an inverse defect spinel. Our study has not confirmed the existence of the previously reported and often recalled defect spinel Zn2Ti3O8.

Optical properties of Eu3+-doped antimony-oxide-based low phonon disordered matrices

A new series of monolithic Eu2O3-doped high antimony oxide (40–80 mol%) content disordered matrices (glasses) of low phonon energy(about 600 cm−1) in the K2O–B2O3–Sb2O3 (KBS) system was prepared by the melt–quench technique. Infrared reflection spectroscopywas used to establish the low phonon energy of the glasses. Amorphicity and devitrificationof the glasses were confirmed by x-ray diffraction analysis. UV–vis absorption spectra ofEu3+ have been measured and the band positions have been justified with quantitative calculation ofthe nephelauxetic parameter and covalent bonding characteristics of the host. TheseEu2O3-doped glasses upon excitation at 393 nm radiation exhibit six emission bands in the range500–750 nm due to their low phonon energy. Of these, the magnetic dipole transition shows small Stark splitting while the electric dipole transition undergoes remarkable Stark splitting into two components. Theyhave been explained by the crystal field effect. The Judd–Ofelt parameters,Ωt = 2,4,6, were also evaluatedand the change of Ωt with the glass composition was correlated with the asymmetric effect atEu3+ ion sites and the fundamental properties like covalent character and opticalbasicity. We are the first to report the spectroscopic properties of theEu3+ ion in KBS low phonon antimony glasses.

Structural and optical properties of Sm(DBM) 3Phen doped in poly(methyl methacrylate) (PMMA): An evidence for cascading energy transfer process

Sm(DBM) 3Phen complexes have been synthesized and studied in detail. X-ray diffraction analysis of Sm(DBM) 3Phen complex reveals crystalline behavior. An enhancement in the fluorescence intensity as compared to the Sm(Phen) 3·2H 2O and Sm(DBM) 3·2H 2O samples has been observed. Stark splitting of the Sm 3+ emission bands has also been observed. The fluorescence decay time for Sm 3+ ( 4G 5/2 → 6H 9/2 transition) is seen to increase from 221.6 μs in Sm 3+ to 232.6 μs in presence of Sm(DBM) 3·2H 2O and to 260.6 μs in Sm(DBM) 3Phen. Energy transfer from excited Phen to DBM and finally from DBM to Sm 3+ is proposed as the cause of the above observations.

Stark splitting of the ground state of Er 3+ in fluorozirconate glass at low temperature

Optical properties of Er 3+-doped ZBLAN glass matrix have been studied by luminescence spectroscopy under 488 nm excitation. The spectrum of the 4S 3/2 4I 15/2 transition, carried out at temperature T = 2 K, shows a new line in the lowest energy region. This new line, centered at 17 996 cm −1, was attributed to the lower transition between the Stark components of the 4S 3/2 4I 15/2 transition. Measurements from T = 2 K to room temperature show the disappearance of this new line. From the results we estimate the splitting of 415 cm −1 for the ground state and 100 cm −1 for the 4S 3/2 excited multiplet. The experimental result allows us to assign the positions of the eight Stark components of the ground state multiplet of the Er 3+ in the ZBLAN glass matrix.

Stark Effect of the RubidiumD2 Line Studied by High-Resolution Laser Spectroscopy

The Stark effect of the 5 s 2 S 1/2 –5 p 2 P 3/2 transition ( D 2 line) of Rb has been studied by high-resolution atomic-beam laser spectroscopy. The splittings of magnetic sublevels of 5 p 2 P 3/2 have been resolved, and the Stark shifts and splittings of the D 2 line have been measured at various electric fields. The scalar polarizability of the D 2 line and the tensor polarizability of the 5 p 2 P 3/2 level have been determined to be α s (5 p 2 P 3/2 ) - α s (5 s 2 S 1/2 ) = 136.95(89) kHz/(kV/cm) 2 and α t (5 p 2 P 3/2 ) = -40.91(38) kHz/(kV/cm) 2 , respectively, by considering the mixing between hyperfine structure levels of 5 p 2 P 3/2 . The precision of α t (5 p 2 P 3/2 ) has been improved by a factor of 2 compared with the previously reported values.

Hollow cathode fall field strength measured by Doppler-free two-photon optogalvanic spectroscopy via Stark splitting of the 2S level of hydrogen

It has recently been demonstrated that Doppler-free two-photon optogalvanic spectroscopy is very well suited to measure the strong electric field strength (0.4 kV/cm to 4 kV/cm) present in the cathode fall of hollow cathode discharges, via the Stark splitting of the 2S level of atomic hydrogen and its isotopes. Based on an improved reliability and precision of the measurements, the aim of the present study is to analyze more deeply the dependence of the cathode fall behaviour for a hydrogen discharge on the usual discharge parameters like gas pressure and discharge current; and for changes of the discharge geometry using two different cathode diameters of 10 mm and 15 mm.

Strong-field terahertz optical sideband generation for wavelength conversion in asymmetric double quantum wells

Terahertz (THz) optical sideband generation in asymmetric double quantum wells in strong THz fields is studied theoretically. Both monotonic THz-power dependence and saturation of the first-order sideband intensity can occur, depending on the near infrared (NIR) and THz photon energies. In both respects the calculated sideband intensity behavior agrees with experimental findings [Appl. Phys. Lett. 75, 2728 (1999); Phys. Rev. B 70, 115312 (2004)]. The nonmonotonic THz-power dependence and saturation of the sideband intensity are due to the excitonic Stark splitting. While the sideband saturation imposes limitations on the wavelength conversion efficiency, the simultaneous broadening of sideband resonances benefits wavelength conversion by increasing the number of NIR frequencies available for wavelength conversion.

Luminescence properties of Pr3+ and Sm3+ ions in natural apatites

The luminescence spectra of Pr3+ and Sm3+ ions in apatite Ca5[F∣(PO4)3] crystals from Spain and Russia have been compared with those for phosphate glasses doped with Pr3+, Sm3+ and Pr3+, Sm3+ ions. Time-resolved spectra measurements confirm that, in apatites, samarium ions occupy two non-equivalent crystal sites; the same is assumed for praseodymium ions. For the first time in minerals, the Stark splitting energy levels ΔE for 3H6 and 1D2 of Pr3+ ion and 6H7/2 of Sm3+ ion were determined. Some small differences in ΔE values for the Spanish and Russian apatite are discussed. The decay times of the excited levels of Pr3+, Sm3+ and Pr3+, Sm3+ doped in phosphate glass were measured at room temperature and at 77 K. The energy transfer process between samarium and praseodymium ions was observed and the energy transfer rate was calculated.