Study on charge transfer interaction and valence state of layered perovskite-type mixed valence complex [NH3(CH2) n NH3]2[(AuII2)(AuIIII4)(I3)2] (n = 7, 8), by means of 197Au Mössbauer spectroscopy

Cs₂[Au^I X ₂][Au^III X ₄](X = Cl, Br, and I) is well known for the three-dimensional perovskite-type gold mixed valence system. Recently, layered perovskite-type gold mixed valence complexes, [NH₃(CH₂) _n NH₃]₂[(Au^II₂)(Au^IIII₄)(I₃)₂] (n = 7 and 8), have been synthesized. We have investigated the relationship between the structural dimensionality and the Au^I–Au^III charge transfer interaction for Cs₂[Au^II₂][Au^IIII₄] and [NH₃(CH₂) _n NH₃]₂[(Au^II₂)(Au^IIII₄)(I₃)₂] (n = 7 and 8) by means of ¹⁹⁷Au Mössbauer spectroscopy.     

Luminescence of Er-doped silicon oxide-zirconia thin films

Er-doped silicon oxide-zirconia thin film samples were prepared by rf co-sputtering. Chemical composition was determined by energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) showed that the films were amorphous. X-ray photoelectron spectroscopy (XPS) measurements showed that the matrix of the films consists of a ZrO₂ main body with pockets of silicon oxide, containing no Si nanoparticles (np) distributed within it. The samples were annealed to 700 °C. Er³⁺: ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, ⁴F_9/2→⁴I_15/2, ⁴I_11/2→⁴I_15/2, and ⁴I_13/2→⁴I_15/2 emissions were observed. Excitation wavelength dependence and excitation photon flux dependence results for the ⁴I_13/2→⁴I_15/2 emission were explained as due to resonant energy transfer from defects in the matrix. ⁴I_11/2→⁴I_15/2 emission dependence on ⁴I_13/2→⁴I_15/2 emission showed that no energy transfer upconversion (ETU) processes were involved and that it was due only to branching from higher levels. ⁴I_13/2→⁴I_15/2 peak intensity decay was interpreted as corresponding to two different populations of Er³⁺ ions. Energy transfer from the defects to the Er ions is very efficient. We concluded that Er-doped silicon oxide-zirconia is a promising material for photonic applications, being excitable at low pumping powers and producing broad-band ⁴I_13/2→⁴I_15/2 emission.     

超导铅膜非平衡相变中准粒子数的变化

本文测量了Pb-I-Pb-I-Pb双隧道结检测结准粒子电流I_t随注入电流I_i的变化。双能隙出现前I_t与I_i近似有抛物线关系,双能隙出现后I_t很快增加。出现双能隙时的l_t与平衡态的I_t⁰之差△I_t在我们的测量温度区间随温度降低而减小。 关键词：     

DIRECT UPCONVERSION SENSITIZATION LUMINESCENCE OF Ho(0.1)Yb(5):OXYFLUORIDE VITROCERAMICS

This paper studies the upconversion luminescence phenomenon of the Ho,Yb co-doped oxyfluoride vitroceramics. There is one group of strong upconversion luminescence lines positioned at 536.5nm, 18639cm^-1; 540.5nm, 18501cm^-1; 544.0nm, 18399cm^-1, which is easily identified as the transitions of ⁵S₂→⁵I₈. There are other splendid upconversion luminescence lines, which are ⁵S₂→⁵I₇,⁵F₅→⁵I₈,⁵G₆→⁵I₈, (⁵G³G)₅ →⁵I₈,(³F³H⁵G)₄→⁵I₇,⁵G₄→⁵I₈ and (⁵G³H)₅→⁵I₈. It is also found that an interesting kind of upconversion cooperative radiation fluorescence comes from a kind of coupling state of clusters consisting of two Yb³⁺ ions.     

Mid-infrared emissions from Ho3+ in Ga2S3-GeS2-Sb2S3 glass

Emission properties were investigated in the infrared region for Ga₂S₃-GeS₂-Sb₂S₃ glasses doped with Ho³⁺. We performed Judd–Ofelt analysis and lifetime measurements of the ⁵I₄, ⁵I₅, and ⁵I₆ levels, which are the initial levels of the mid-infrared emissions between 3 to 5 μm of Ho³⁺. The quantum efficiencies reached approximately 18%, 64%, and ～100% for the ⁵I₄, ⁵I₅, and ⁵I₆, respectively. Population analyses were carried out from the relative intensities of the emissions in the near-infrared region. We investigated the dependences on the Ho³⁺ ion concentration of the population ratio of the initial levels to the final levels, [initial]/[final], of the mid-infrared emissions. The population ratio of [⁵I₅]/[⁵I₆] decreased with increase of the Ho³⁺ concentration while those of [⁵I₄]/[⁵I₅] and [⁵I₆]/[⁵I₇] increased. Particularly, the former, [⁵I₄]/[⁵I₅], rapidly increased because of the strong concentration quenching of the ⁵I₅ level through cross relaxation. It was found that the population inversion for the 4.8 μm emission due to the transition, ⁵I₄→⁵I₅, was achieved at high Ho³⁺ concentration in the present experiments.     

Luminescence of rare earth-doped Si–ZrO2 co-sputtered films

Er-doped Si-yttria-stabilized zirconia (YSZ) thin film samples were prepared by rf co-sputtering. Chemical composition of the samples was determined using energy-dispersive spectroscopy (EDS) and the structure of the films by X-ray diffraction (XRD). The samples were annealed to 700 °C. Photoluminescence (PL) measurements were performed for the visible and infrared. By exciting with the 488-nm-laser line the Er³⁺ emissions ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, ⁴F_9/2→⁴I_15/2 and a narrow ⁴I_13/2→⁴I_15/2 emission were observed. The ⁴I_11/2→⁴I_15/2 emissions for the same excitation wavelength were weak. Excitation wavelength dependence of the ⁴I_13/2→⁴I_15/2 emissions indicated that the emissions were due to a combination of energy transfer from Si nanoparticles (np) to Er ions and energy transfer from defects in the matrix to the Er ions for excitations resonant with the energy levels of such defects. ⁴I_13/2→⁴I_15/2 emission decay measurements show two decaying populations of Er ions according to their locations with respect to other ions or any non-radiative defects. ⁴I_11/2→⁴I_15/2 emission dependence on ⁴I_13/2→⁴I_15/2 emission showed that the former was possibly due to a combination of downconversion from higher levels of the Er ions, energy transfer from Si nanoparticles and upconversion transfer processes. We concluded that Er-doped Si-YSZ is a promising material for photonic applications being easily broadband excited using low-pumping powers.     

NMR-ON measurements of123, 124, 131I in nickel

The magnetic hyperfine splitting frequencies of¹²³INi,¹²⁴INi and¹³¹INi in a zero external magnetic field have been determined by the NMR-ON method as 258.9(1), 165.9(1) and 179.5(2) MHz, respectively. With the known values of the magnetic moments, the magnetic hyperfine fields have been deduced:B _HF(¹²³INi)=30.17(5) T,B _HF(¹²⁴INi)=30.14(9) T,B _HF(¹³¹INi)=30.06(4) T; the weighted average isB _HF(INi)=30.11(4) T. The small difference of theB _HF(¹³¹INi) with those of¹²³INi and¹²⁴INi is discussed comparing with results of the hyperfine splitting frequency of iodine in iron host.     

Tunable upconversion in Er-doped orthorhombic lead fluoride compound

Near infrared-visible upconversion in Er³⁺ doped orthorhombic PbF₂ compound is investigated. It is experimentally observed that the red emission intensity increases monotonously with Er³⁺ concentration increase, while the green emission intensity first increases and then decreases. Based on the rate-equation, the energy transfers involved in the upconversion processes have been explored. It is shown that due to the different multipolar nature for the energy transfer processes of ²H_11/2 (⁴S_3/2)+⁴I_15/2→⁴I_9/2+⁴I_13/2 and ⁴I_11/2+⁴I_11/2→⁴F_7/2+⁴I_15/2, the green and red upconversion emissions depend on Er³⁺ concentration in different ways. The theoretical results are in good agreement with the experimental observation. It is shown that the upconverted emission bands can be tuned by controlling Er³⁺ concentration in orthorhombic PbF₂ compound, which has many photonic applications under NIR excitation.     

Hyperfine patterns of infrared absorption lines of Ho3+ C4v centres in CaF2

Hyperfine structure is observed on several infrared transitions to the ⁵I₇ and ⁵I₆ multiplets of the Ho³⁺ C_4v centre in CaF₂. Particularly complex and detailed hyperfine structures are observed for transitions to the Y₃ level of the ⁵I₇ multiplet, which include the appearance of ΔI_z ≠ 0 transitions. The hyperfine lines of this level are satisfactorily accounted for by strong mixing of close-lying levels of this multiplet by the perpendicular hyperfine interaction, which leads to relaxation of the ΔI_z = 0 selection rule and a redistribution of the hyperfine intensities over many transitions. An excellent correspondence is found between the measured and simulated spectra.     

Exciton molecule in semiconductors by phonon-assisted two-photon absorption

Direct creation of bi-excitonic states by photon-assisted two-photon absorption in indirect-gap semiconductors is investigated theoretically. The symmetry of the indirect bi-exciton states and of the phonon used are given for the case of Ge. A numerical application to the case of Si shows that the indirect two-photon absorption coefficient for bi-excitonic α²_I (bi-ex) transitions is several orders of magnitude larger than both indirect two-photon interband, α²_I (band), and excitonic, α²_I (exc), transitions. It becomes smaller than both indirect one-photon interband, α¹_I (band), and excitonic, α¹_I (exc), transitions for available laser intensities. The essential contribution to this enhancement of α²_I (bi-ex) is found to be from the resonance effect in the first process and from both the resonance effect and matrix elements included in the second process.     

Photoluminescence of Er-doped Si-SiO2 and Al–Si-SiO2 sputtered thin films

Er-doped Si-SiO₂ and Al–Si-SiO₂ films have been deposited by rf-sputtering being annealed afterwards. Annealing behavior of the Er³⁺: ⁴I_13/2→⁴I_15/2 emission of Er-doped Si-SiO₂ yields a maximum intensity for annealing at 700–800 °C. ⁴I_13/2→⁴I_15/2 peak emission for Er-doped Al–Si-SiO₂ at 1525 nm is shifted from that for Er-doped Si-SiO₂ at 1530 nm and the bandwidth increases from 29 to 42 nm. ⁴I_13/2→⁴I_15/2 emission decays present a fast decaying component related to Er ions coupled to Si nanoparticles, defects, or other ions, and a slow decaying component related to isolated Er ions. Excitation wavelength dependence and excitation power dependence for the ⁴I_13/2→⁴I_15/2 emission correspond with energy transfer from Si nanoparticles. Populating of the ⁴I_11/2 level in Er-doped Si-SiO₂ involves branching and energy transfer upconversion involving two or more Er ions. Addition of Al reduces the populating of this level to an energy transfer upconversion involving two ions.     

Optical character of Er/Yb co-doped P2O5-CaO-Na2O-Al2O3-AgO phosphate glass

The up-conversion (UC) and near infrared (NIR) luminescence of Er³⁺/Yb³⁺ co-doped phosphate glass are investigated. In the UC emission range, the 523 nm, 546 nm green emissions and the 659 nm red emission are observed. With the increasing pump power, the intensity ratios of I₅₂₃/I₆₅₉, I₅₄₆/I₆₅₉ and I₅₂₃/I₅₄₆ increase gradually. The phenomenon is reasonably interpreted by theoretical analysis based on steady state rate equations. The emission cross section of the infrared emission at 1546 nm is larger (about 6.7 × 10^− 21 cm²), which is suitable for making fiber amplifier.     

Effects of different ions implantation on yellow luminescence from GaN

The influence of C, N, O, Mg, Si and co-implants (Mg+Si) ions implantation with fluences in the wide range 10¹³-10¹⁷ cm⁻² on the yellow luminescence (YL) properties of wurtzite GaN has been studied by photoluminescence (PL) spectroscopy. Two types of n-type GaN samples grown by metal-organic chemical vapor deposition method (MOCVD) and labeled as No-1 and No-2 were studied. In their as-grown states, No-1 samples had strong YL, while No-2 samples had weak YL. Results of the frontside and backside PL measurements in one of the as-grown GaN epifilms are also presented. Comparing the intensity of YL between frontside and backside PL spectra, the backside PL spectrum shows the more intense YL intensity. This implies that most of the intrinsic defects giving rise to YL exist mainly near the interface between the epilayer and buffer layer. Our experimental results show that the intensity ratio of YL to near-band-edge UV emission (I_YL/I_UV) decreases gradually by increasing the C implantation fluence from 10¹³ to 10¹⁶ cm⁻² for No-1 samples after annealing at 900 °C. When the fluence is 10¹⁷ cm⁻², a distinct change of the I_YL/I_UV is observed, which is strongly increased after annealing. For No-2 samples, after annealing the I_YL/I_UV decreases gradually with increase in the C implantation fluence from 10¹³ to 10¹⁵ cm⁻². The I_YL/I_UV is gradually increased with increasing C fluence from 10¹⁶ to 10¹⁷ cm⁻² after annealing, while I_YL/I_UV for other ions-implanted GaN samples decreases monotonically with increase in the ions implantation fluences from 10¹³ to 10¹⁷ cm⁻² for both No-1 samples and No-2 samples. It is noted that for annealed C-implanted No-2 samples I_YL/I_UV is much higher than that of the as-grown one and other ion-implanted ones. In addition, I_YL/I_UV for the Mg, Si, and co-implants (Mg+Si) implanted No-2 samples with a fluence of 10¹³ cm⁻² after being annealed at 900 °C is higher than that of the as-grown one. Based on our experimental data and literature results reported previously, the origins of the YL band have been discussed.     

Excited states dynamics of Er3+ in Sc2O3 ceramic

The spectral characteristics of Er³⁺ in Sc₂O₃ transparent ceramics are presented. The Er³⁺ visible spectra in the ceramics, prepared by solid-state synthesis, show only lines that could be assigned to C₂ sites. The Stark energy levels, cross-sections and emission kinetics of levels involved in the green upconversion emission under infrared excitation in the 800 nm range were determined. The green upconversion emission (²H_11/2, ⁴S_3/2)→⁴I_15/2 characteristics under excitation with a pulsed Ti:sapphire laser in (⁴I_15/2→⁴I_9/2) absorption were analyzed. The emission kinetics reveal a competition of two-step (⁴I_15/2→⁴I_9/2)+(⁴I_9/2→²H_9/2) excited state absorption (ESA) and (⁴I_11/2, ⁴I_15/2)→(⁴I_11/2, ⁴F_7/2) energy transfer upconversion (ETU) processes function on the excitation wavelength.     

Emission Spectroscopic Investigation of the Decomposition of CCl4 in Plasma Etching Processes

The CCl₄ plasma decomposition and the etching of SiO₂ and Al by the CCl₄ plasma is investigated with the aid of emission intensity Iλ of such species as Cl₂, CCl, Cl and CO, which are influenced systematically by the etching process. A time independent electron density (n_e ≈ 2 · 10⁸ ?1 · 10¹⁰ cm^?3, dependent on plasma conditions) is measured by microwave diagnostics. The ratio Iλ/n_e and Iλ/I_reference' resp. (I_reference = I_Helium) is a relative measure of concentrations. The ratio I_cl2/I_ccl is very sensitive against CCl₄-decomposition and etching processes of SiO₂ and Al. Its changes during the etching process of SiO₂ and Al in a CCl₄ plasma are investigated.     

He(I) photoelectron spectroscopy of anions in adiponitrile solution

He(I) photoelectron spectra are reported of solutions of salts in adiponitrile in which peaks characteristic of the anions are visible; the vertical ionisation energies of these peaks are 6.91 and 7.85 (I^?), 7.6 (Br^?), 8.1 (Cl^?), 7.0 (CNS^?), 8.1 and 6.8 (NO₂^?), and 7.6eV (SO₄^2?). The salts examined were tetra-n-butyl ammonium (NO₂^?, I^?, Br^?, Cl^?, CNS^?, SO₄^2?), N-methylpyridinium I^?, trimethylphenylammonium I^?, choline I^?, methyltrioctylammonium I^? and methyltriphenylphosphonium Br^?. The relationship between these spectra and the charge transfer to solvent spectra of the anions is discussed.     

Light polarization in iodine-doped polyvinyl alcohol films

¹²⁹I Mössbauer measurements have been performed on unidirectionally stretched iodinedoped polyvinyl alcohol(PVA) films which are widely used as optical polarizers. In the films iodine is observed to be in the form of I^?, I ₃ ^? , and I ₅ ^? and the stretch of the films increases the abundance of the polyiodides, I ₃ ^? and I ₅ ^? . In the stretched PVA films, it has become clear that the linear polyiodides lie parallel to the stretching direction.     

Hyperfine splittings of infrared lines of the cubic centre in CaF2:Ho3+

Hyperfine structure is observed on three transitions of the ⁵I₈?→?⁵I₇ absorption spectrum of the cubic-symmetry centre in CaF₂:Ho³⁺. Hyperfine mixing between the two lowest levels of the ⁵I₈ ground multiplet produces a complex and rich spectrum, which is only partially resolved. Simulated spectra are generated using one parameter to determine electronic crystal-field wavefunctions and one for the crystal-field splitting of the near-degenerate ground state. The simulated spectra correspond well with the measured spectra and demonstrate that the complex structure is well accounted for by dipole-hyperfine mixing between the lowest triplet and doublet states in the ⁵I₈ ground multiplet.     

Spectral broadening and luminescence quenching of 1.53 μm emission in Er-doped zinc tellurite glass

The emission spectra and the lifetime of the lasing transition ⁴I_13/2→⁴I_15/2 in Er³⁺-doped TeO₂-ZnO binary glass have been studied. The investigation includes Raman scattering spectroscopy as well as optical absorption, luminescence, and lifetime measurements techniques. The influence of erbium concentration on the line-shape of this electron transition has been analyzed. It was observed that the increasing of Er³⁺ ion concentration, in the 0.2-4 mol% range, results in a structural changes and a significant spectral broadening of the 1.53 μm emission band. Reabsorption has been evoked to explain the broadening of the ⁴I_13/2→⁴I_15/2 emission line. In the paper, is also reported the effect of the erbium content on the emission intensity of the ⁴I_13/2→⁴I_15/2 transition as well as on the lifetime of the ⁴I_13/2 level. Based on the electrical-dipole interaction theory, the luminescence concentration quenching mechanism by hydroxyl groups is analyzed. The data suggest that <10% of hydroxyl groups are coupled to erbium ions in the zinc tellurite glass network.     

低温下Er3+/Yb3+共掺碲酸盐玻璃的发光特性研究

研究了在8—300K温度范围中, Er³⁺/Yb³⁺共掺碲酸盐玻璃的15μm荧光光谱、上转换光谱与温度的关系. Er³⁺:⁴I_13/2→⁴I_15/2跃迁发射光谱通过高斯拟合和简单的四能级系统估计了Er³⁺离子⁴I_13/2和⁴ 关键词： 碲酸盐玻璃 上转换发光 低温 荧光特性