Optical delay with spectral hole burning in Doppler-broadened cesium vapor

The full frequency dependence of the optical delay in the Cs D₁ (6 ²S_1/2 ? 6 ²P_1/2) line has been observed, including all four hyperfine split components. Pulse delays of 1.6 ns to 24.1 ns are obtained by scanning across the hyperfine splitting associated with the lower ²S_1/2 state. Optical control of pulse delays in cesium vapor was demonstrated by pumping the D₂ (6 ²S_1/2 ? 6 ²P_3/2) transition and observing resulting holes in the D₁ delay spectrum. For a pump at four times the saturation intensity, the pulse delays are reduced by a maximum of 78% in a narrow region of 110 MHz. The frequency dependence of the delays of the probe laser in the vicinity of the spectral holes agrees with a Kramers–Kronig model prediction.     

Enhanced OH radical generation by dual-frequency ultrasound with TiO2 nanoparticles: Its application to targeted sonodynamic therapy

The present study demonstrated the enhanced hydroxyl (OH) radical generation by combined use of dual-frequency (0.5 MHz and 1 MHz) ultrasound (US) and titanium dioxide (TiO₂) nanoparticles (NPs) as sonocatalyst. The OH radical generation became the maximum, when 0.5 MHz US was irradiated at an intensity of 0.8 W/cm² and 1 MHz US was irradiated at intensities at 0.4 W/cm² in the presence of TiO₂ NPs under the examined conditions. After incorporation of TiO₂ NPs modified with targeting protein pre-S1/S2, HepG2 cancer cells were subjected to the dual-frequency US at optimum irradiation intensities (“targeted-TiO₂/dual-US treatment”). Growth of the HepG2 cells was reduced by 46% compared with the control condition after irradiation of dual-frequency US for 60 s with TiO₂ NPs incorporation. In contrast, HepG2 cell growth was almost the same as that in the control condition when cells were irradiated with either 0.5 MHz or 1 MHz ultrasound alone without TiO₂ NP incorporation.     

Electronic charge transfer between Au nano-particles and TiO2-terminated SrTiO3(0 0 1) substrate

The interaction between Au nano-particles and oxide supports is recently discussed in terms of the catalytic activities. This paper reports the electronic charge transfer between Au nano-particles and TiO₂-terminated SrTiO₃(0 0 1) substrate, which is compared with that for stoichiometric(S)-, pseudo-stoichiometric(S¹)- and reduced(R)-TiO₂(1 1 0) supports. We observed the photoelectron spectra of Au 4f, O 2s, Ti 3p, and Sr 4p lines and also measured the work functions for Au/oxides supports using synchrotron-radiation light. As the results, all the O 2s, Ti 3p, and Sr 4p lines for Au/SrTiO₃(0 0 1) show lower binding energy shifts in a quite same manner and abrupt increase in the work function is seen in an initial stage. This clearly evidences an electronic charge transfer from the substrate to Au probably due to a much larger work function of Au than SrTiO₃(0 0 1), which leads to an upward band bending (0.3 eV) just like a Schottky contact. Electronic charge transfers also take place at Au/S- and Au/S¹-TiO₂(1 1 0) and Au/R-TiO₂(1 1 0) interfaces, where electrons are transferred from Au to S- and S¹-TiO₂ and from R-TiO₂ to Au, as predicted by ab initio calculations.     

Absolute frequency and isotope shift measurements of the cooling transition in singly ionized indium

We report greater than two orders of magnitude improvements in the absolute frequency and isotope shift measurements of the In⁺ 5s^{2 1}S₀ (F = 9/2)–5s5p ³P₁ (F = 11/2) transition near 230.6 nm. The laser-induced fluorescence from a single In⁺ in a radio-frequency trap is detected. The fourth-harmonic of a semiconductor laser is used as the light source. The absolute frequency is measured with the help of a frequency comb referenced to a Cs atomic clock. The resulting transition frequencies for isotopes ¹¹⁵In⁺ and ¹¹³In⁺ are measured to be 1 299 648 954.54(10) MHz and 1 299 649 585.36(16) MHz, respectively. The deduced cooling transition frequency difference is 630.82(19) MHz. By taking into account of the hyperfine interaction, the isotope shift is calculated to be 695.76(1.68) MHz.     

Continuous measurements of stable carbon isotopes in CO2 with a near-IR laser absorption spectrometer

A near-IR laser absorption spectrometer using a technique of wavelength modulation spectroscopy is used to measure stable carbon isotope ratios of ambient CO₂ (δ¹³C) via the absorption lines ¹²CO₂ R(17) (2ν₁ + ν¹₂ − ν¹₂ + ν₃) at 4978.205 cm⁻¹ and ¹³CO₂ P(16) (ν₁ + 2ν₂ + ν₃) at 4978.023 cm⁻¹. The isotope ratios are measured with a reproducibility of 0.02‰ (1σ) in a 130-s integration time over a 12-h period. The humidity effect on δ¹³C values has been evaluated in laboratory experiments. The δ¹³C values of CO₂ in ambient air were measured continuously over 8 days and agreed well with those from isotope ratio mass spectrometry of canister samples. The spectrometer is thus capable of real-time, in situ measurements of stable carbon isotope ratios of CO₂ under ambient conditions.     

Stark and Frequency Measurements in the FIR Spectrum of H2O2

The submillimeter-wave spectrum of H₂O₂has been recorded by means of a tunable FIR spectrometer. Stark measurements have been performed on three selected transitions in then= 0 state, namely, the 2₂₀–1₁₀(τ = 4 ← 2) at 1 272 297 MHz, the 8₂₆–7₁₆(τ = 1 ← 3) at 882 451 MHz, and the 9₂₈–8₁₈(τ = 1 ← 3) at 962 933 MHz. Accurate values of the transition dipole moments of the molecule have been derived by considering the interaction between the levels involved in the transition and the close near-resonant levels. About 40 new lines, belonging to the^rQ₄and^rQ₅subbranches of the rotational transitions between the lowest torsional states (τ = 1, 2, 3, 4n= 0), have been measured in the 2.8 and 3.4 THz spectral regions and analyzed together with the previously measured millimeter- and submillimeter-wave, as well as IR, transitions.     

1H NMR study of proton dynamics in (NH4)3H(SO4)2

Proton dynamics in (NH₄)₃H(SO₄)₂ has been studied by means of ¹H solid-state NMR. The ¹H magic-angle-spinning (MAS) NMR spectra were traced at room temperature (RT) and at Larmor frequency of 400.13 MHz. ¹H static NMR spectra were measured at 200.13 MHz in the range of 135–490 K. ¹H spin-lattice relaxation times, T₁, were measured at 200.13 and 19.65 MHz in the ranges of 135–490 and 153–456 K, respectively. The ¹H chemical shift for the acidic proton (14.7 ppm) indicates strong hydrogen bonds. In phase III, NH₄⁺ reorientation takes place; one type of NH₄⁺ ions reorients with an activation energy (E_a) of 14 kJ mol^− 1 and the inverse of a frequency factor (τ₀) of 0.85 × 10^− 14 s. In phase II, a very fast local and anisotropic motion of the acidic protons takes place. NH₄⁺ ions start to diffuse translationally, and no proton exchange is observed between NH₄⁺ ions and the acidic protons. In phase I, both NH₄⁺ ions and the acidic protons diffuse translationally. The acidic protons diffuse with parameters of E_a = 27 kJ mol^− 1 and τ₀ = 4.2 × 10^− 13 s. The translational diffusion of the acidic protons is responsible for the macroscopic proton conductivity, as the NH₄⁺ translational diffusion is slow and proton exchange between NH₄⁺ ions and the acidic protons is negligible.     

Hyperfine interactions in magnetoelectric hexaferrite system

Nuclear magnetic resonance (NMR) in Y-hexaferrite system (Ba_1?xSr_x)₂Zn₂Fe₁₂O₂₂ was measured on both monocrystalline and polycrystalline samples at liquid helium temperature. Corresponding ab-initio calculation of the hyperfine parameters was also performed. The signal from ⁵⁷Fe was detected in the frequency interval 65–76 MHz, while NMR spectrum of ⁶⁷Zn nuclei occurs between 15 and 30 MHz. Due to the disorder in two tetrahedral sublattices occupied partly by Zn and partly by Fe, the NMR lines are broad and the spectra are poorly resolved. Comparison between the experimentally observed ⁶⁷Zn spectra and the spectra modelled using the calculated hyperfine parameters was made. It indicates that the spectra of ⁶⁷Zn can be used to determine the distribution of Zn and Fe between the two tetrahedral sublattices.     

Ultraviolet spectroscopy of Pr+3 and its use in making ultraviolet filters

Sputtered deposited thin films of AlN:Pr and GaN:Pr emit in ultraviolet–visible and visible regions of the spectrum, respectively, under electron excitation in cathodoluminescence apparatus. The goal is to study the ultraviolet emission from Pr⁺³ when doped in nitride semiconductor hosts. Luminescence peaks at a wavelength of 295 nm (4.2 eV), 335 nm (3.7 eV) and 385 nm (3.24 eV) are observed as a result from ¹S₀ → ¹G₄, ¹S₀ → ¹D₂ and ¹S₀ → ¹I₆ transitions, respectively. However the ¹S₀ → ¹G₄ and ¹S₀ → ¹D₂ transitions are not observed when Pr⁺³ is doped in GaN host. The bandgap of GaN absorbs the ultraviolet radiation emitted from Pr⁺³ and hence GaN can be used as ultraviolet filter for radiation shielding and protection purposes. AlN is transparent to ultraviolet due to its wide bandgap of 6.2 eV.     

Sonocatalytic injury of cancer cells attached on the surface of a nickel–titanium dioxide alloy plate

The present study demonstrates ultrasound-induced cell injury using a nickel–titanium dioxide (Ni–TiO₂) alloy plate as a sonocatalyst and a cell culture surface. Ultrasound irradiation of cell-free Ni–TiO₂ alloy plates with 1 MHz ultrasound at 0.5 W/cm² for 30 s led to an increased generation of hydroxyl (OH) radicals compared to nickel–titanium (Ni–Ti) control alloy plates with and without ultrasound irradiation. When human breast cancer cells (MCF-7 cells) cultured on the Ni–TiO₂ alloy plates were irradiated with 1 MHz ultrasound at 0.5 W/cm² for 30 s and then incubated for 48 h, cell density on the alloy plate was reduced to approximately 50% of the controls on the Ni–Ti alloy plates with and without ultrasound irradiation. These results indicate the injury of MCF-7 cells following sonocatalytic OH radical generation by Ni–TiO₂. Further experiments demonstrated cell shrinkage and chromatin condensation after ultrasound irradiation of MCF-7 cells attached on the Ni–TiO₂ alloy plates, indicating induction of apoptosis.     

Ferromagnetic order and spin-glass behavior in multi-metallic compound Ni1.125Co0.375[Fe(CN)6] · 6.8H2O

Multi-metallic Prussian blue compound Ni_1.125Co_0.375[Fe(CN)₆] · 6.8H₂O has been synthesized. The Mössbauer spectroscopy at room temperature and IR spectra study revealed that the metal ions are bonded through cyanide ligand and the presence of low spin Fe^III(S = 1/2) and high spin Fe^III(S = 5/2) ions, as showed in these structure: Fe^III(S = 1/2)-CN-(Co^II/Ni^II)(96%) and Fe^III(S = 5/2)-NC-(Co^II/Ni^II) (4%). The Curie constant of C = 3.00 cm³ K mol⁻¹ and Weiss paramagnetic Curie temperature of θ = 16.43 K were observed in fitting according to Curie–Weiss law. These results indicate that there existed a ferromagnetic exchange interaction in the complexes. The observed value of coercive field (H_c) and remanent magnetization (M_r) at 4 K for the compound are 497 Oe and 1.03 Nβ. The presence of spin-glass behaviours in the compound is ascribed mainly to domain mobility or domain growth under different cooling conditions.     

First analysis of the 3ν9−ν9 hot band of difluoroboric acid (BF2OH). Further evidence of large amplitude effects for the OH torsion

The hot band 3ν₉?ν₉ of the isotopologue ¹¹BF₂OH (difluoroboric acid) located at 1034.78 cm^?1 was investigated for the first time by Fourier transform infrared spectroscopy. During previous studies both, the ν₉ mode (OH-torsion relative to the BF₂ moiety, at 522.87 cm^?1) and the ν₄ mode (in-plane OH bend) had been shown to exert large amplitude motion, and splittings of 0.0051 and 0.0038 cm^?1 had been observed in the interacting 2ν₉ and ν₄ bands located at 1042.87 and 961.49 cm^?1, respectively. The present work establishes large amplitude effects also for the 9³ excited state located at 1557.655 cm^?1. Numerous P and R transitions of the 3ν₉–ν₉ hot band were identified in the 2ν₉ manifold, and doublets corresponding to a torsional splitting of 0.031 cm^?1 in the 9³ state were observed. The vibrational assignment of the 9³ state was confirmed by the detection of the 3ν₉?2ν₉ hot band Q branch in the 19 μm region.     

A Boubaker polynomials expansion scheme (BPES)-related protocol for measuring sprayed thin films thermal characteristics

Measurements of In₂S₃ and ZnIn₂S₄ sprayed thin films thermal characteristics have been carried out using the photodetection technique. The thermal conductivity k and diffusivity D were obtained using a new protocol based on photothermal signal parameters analysis. Measured values of k and D were respectively, (15.2 ± 0.85) W m⁻¹K⁻¹ and (69.8 ± 7.1) × 10⁻⁶ m²s⁻¹ for In₂S₃, (7.2 ± 0.7) W m⁻¹K⁻¹ and (32.7 ± 4.3) × 10⁻⁶ m²s⁻¹ for ZnIn₂S₄. These values are extremely important since similar compounds are more and more proposed as Cd-free alternative materials for solar cells buffer layers.     

Submillimeter-wave measurements of N2 and O2 pressure broadening for HO2 radical generated by Hg-photosensitized reaction

The N₂ and O₂ pressure broadening coefficients of the pure rotational transitions at 625.66 GHz (N_KaKc=10_1?9–10_0?10, J=10.5–10.5) and 649.70 GHz (N_KaKc=10_2?9–9_2?8, J=9.5–8.5) in the vibronic ground state X²A′ of the perhydroxyl (HO₂) radical have been determined by precise laboratory measurements. For the production of HO₂, the mercury-photosensitized reaction of the H₂ and O₂ precursors was used to provide an optimum condition for measurement of the pressure broadening coefficient. The Superconducting Submillimeter-wave Limb Emission Sounder (SMILES) was designed to monitor the volume mixing ratio of trace gases including HO₂ in the Earth's upper atmosphere using these transitions. The precise measurement of pressure broadening coefficient γ in terms of the half width at half maximum is required in order to retrieve the atmospheric volume mixing ratio. In this work, γ coefficients of the 625.66 GHz transition were determined for N₂ and O₂ at room temperature as γ(N₂)=4.085±0.049 MHz/Torr and γ(O₂)=2.578±0.047 MHz/Torr with 3σ uncertainty. Similarly, the coefficients of the 649.70 GHz transition were determined as γ(N₂)=3.489±0.094 MHz/Torr and γ(O₂)=2.615±0.099 MHz/Torr. The air broadening coefficients for the 625.66 GHz and 649.70 GHz lines were estimated at γ(air)=3.769±0.067 MHz and 3.298±0.099 MHz respectively, where the uncertainty includes possible systematic errors. The newly determined coefficients are compared with previous results and we discuss the advantage of the mercury-photosensitized reaction for HO₂ generation. In comparison with those of other singlet molecules, the pressure broadening coefficients of the HO₂ radical are not much affected by the existence of an unpaired electron.     

High-energy ion induced physical and surface modifications in antimony sulphide thin films

Sb₂S₃ thin films prepared by electrodeposition on indium tin oxide coated glass substrate were irradiated with 150 MeV Ni¹¹⁺ ions for various fluence in the range of 10¹¹–10¹³ ions/cm². The modifications in the structure, surface morphology and optical properties have been studied as a function of ion fluence. X-ray diffraction (XRD) analysis indicates a shift in the (2 4 0) peak position towards lower diffraction angle and a decrease in grain size with increase in ion fluence. Presence of microcracks due to irradiation induced grain splitting effect has been observed from the SEM micrograph at higher ion fluence. The optical absorbance spectrum revealed a shift in the fundamental absorption edge and the band gap energy increased from a value of 1.63 eV for as-deposited films to 1.80 eV for the films irradiated with 10¹³ ions/cm².     

The local structure of Cs(I) and Cs(II) in a Cs2ZnCl4 single crystal studied by nuclear magnetic resonance

The rotation patterns of the ¹³³Cs (I=7/2) nuclear magnetic resonance (NMR) in a Cs₂ZnCl₄ single crystal grown by using the slow evaporation method were measured in two mutually perpendicular crystal planes. Two different groups of Cs resonances were recorded; this result points to the existence of two types of crystallographically inequivalent Cs(I) and Cs(II). The angular dependences of the NMR spectra led to different values for the quadrupole coupling constants and asymmetry parameters: e²qQ/h=148 kHz and η=0.11 for the Cs(I) ion, and e²qQ/h=274 kHz and η=0.66 for the Cs(II) ion. The EFG tensors of Cs(I) and Cs(II) are asymmetric, and the orientations of the principal axes of the EFG tensors do not coincide. Only, the principal Y-axes of the EFG tensors coincide for the Cs(I) and Cs(II) sites. The Cs(I) ion is surrounded by 11 chlorine ions, making it rather free and high in symmetry. The Cs(II) ion has only nine neighbors and seems to be more tight than the Cs(I) ion.     

Paramagnetic properties of the spinel-type Al1−xMnx-sulphate salts for its pillared intercalation into a clay mineral

Paramagnetic interactions on Manganese ions substituted for Aluminium ions by x-mole fraction (x=0.01–0.1) for the spinel-type Al-complexes, [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺, were investigated. The superconducting quantum interference detection (SQUID) measurements showed a small susceptibility of the order of 10⁻⁶ emu/g originated from the Mn ion, and from the saturation value of the DC-magnetization for the 10 mol% Mn concentration, the spin S-value was determined as 2.8 close to its divalent state spin 5/2. The 9 GHz electron paramagnetic resonance (EPR) study revealed that the number of Mn²⁺ ions embedded in the axial crystal field had a characteristic maximum at the stoichiometric molar concentration Al/(Al+Al₁₂) equal to 7.69%, and the Infrared absorption (IR) experimental result verified this evidence. A theoretical approach was made separately for the concentrations below and above 7.69%. The higher-frequency 24 and 97 GHz EPR measurements examined effectively the result of the crystal field analysis in the 9 GHz, except for the small line splittings due to the higher-order Zeeman and hyperfine effects of the S-state ion. The intercalation of Al_1−xMn_x-sulphate (x=0.07) as a pillaring agent into a clay mineral, montmorillonite, was confirmed from the X-ray diffraction results.     

Feasibility of arsenic and antimony NMR spectroscopy in solids: An investigation of some group 15 compounds

The feasibility of obtaining ⁷⁵As and ^121/123Sb NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, ^121/123Sb NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide “salts” are reflected in the measured ⁷⁵As and ¹²¹Sb nuclear quadrupole coupling constants, C_Q(⁷⁵As)=7.8 MHz and C_Q(¹²¹Sb)=159 MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of ⁷⁵As and ¹²¹Sb NMR spectra (at 154 and 215 MHz, respectively, i.e., at B₀=21.14 T) with linewidths in excess of 1 MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG).     

High temperature protonic conduction in Sr-doped LaP3O9

Electrical conduction of Sr-doped LaP₃O₉ ([Sr]/{[La] + [Sr]} = 2–10 mol%) was investigated under 0.4–5 kPa of p(H₂O) and 0.01–100 kPa of p(O₂) or 0.3–3 kPa of p(H₂) at 573–973 K. Sr-doped LaP₃O₉ showed apparent H/D isotope effect on conductivity regardless of the Sr-doping level under both H₂O/O₂ oxidizing and H₂/H₂O reducing conditions at investigated temperatures. Conductivities of the material were almost independent of p(O₂) and p(H₂O). These results demonstrated that the Sr-doped LaP₃O₉ exhibited protonic conduction under wide ranges of p(O₂), p(H₂O) and temperature. The conductivity of the Sr-doped LaP₃O₉ increased with increasing Sr concentration up to its solubility limit, ca. 3 mol%, while the further Sr-doping slightly degraded the conductivity. These indicate that Sr²⁺ substitution for La³⁺ leads to proton dissolution into the material and induced protonic conduction. Conductivities of the 3 mol% Sr-doped sample were 2 × 10^- 6–5 × 10^− 4 S cm^− 1 at 573–973 K.     

The thermopower of transition-metal double-perovskites: A sensitive probe of their electronic structures around the Fermi level

We report on a comparative study of S(T) for a series of transition-metal double-perovskites A₂BB′O₆ (A – Ca, Sr, Ba, and B, B′ = transition metal ions), some of them known to have half-metallic ground states. For Sr₂BB′O₆ with BB′ = CrMo, CrW, CrRe, FeMo, and FeRe (ferrimagnetic with high Curie temperatures), S(T) is metallic, for B′ = Mo and W it is n-type and for B′ =  Re, p-type. For A₂FeMoO₆ (A = Ca, Sr, Ba), the crystallographic differences (monoclinic, tetragonal and cubic space-groups, respectively) are accompanied by prominent differences in their (metallic) S(T). For the insulating Sr₂MnReO₆ and Ba₂MnReO₆, the onset of ferromagnetic order below T_c ∼ 120 K is marked by a steep drop of S(T) accompanied by only a slight change in the slope of ln ρ versus 1/T^1/2. Significant conclusions were drawn from the experimental results without the need for elaborate models.