Laser atomic photoionization spectral analysis of element traces

A new method for determining trace amounts of elements in a substance has been developed. It is based on thermal evaporation and atomization of a substance in vacuum and detection of the released trace atoms by the laser stepwise photoionization technique. A rather effective way of detecting atoms is their multistep excitation to Rydberg states by the radiation of tunable dye lasers with their subsequent ionization by electric field pulses. The analytical laser spectrometer consisting of several tunable, pulsed dye lasers, a vacuum chamber with an atomizer and a recording system is described. The microimpurities of elements have been detected in pure materials: the contents of Na impurities in CdS crystals (2×10^?6%) and Al impurities in germanium (2×10^?7%). The detection limit of about 10^?9% was determined. A technique for direct determination of the content of elements in natural water and human blood is described. A high sensitivity, universality and other merits of the method enable it to be used in determining traces of many important elements at a level of 10^?8 to 10^?11% almost in any matrix.     

Measurement of collision broadening of the calcium resonance line by low resolution spectroscopy

The Lorentzian half-widths of the Ca λ4227 Å (4s²¹S₀?4s4p¹P₁) line in the impact regime have been measured by low resolution spectroscopy. They were determined from measurements of the total absorption of both a white source and an emission line of the same transition. The absorption cells contained calcium at about 410°C with a perturbing gas of argon at pressures of up to about 50 cm of Hg. Corrections were applied to account for the width of the emission line and the non-transparency of the absorption cells. High resolution measurements of absorption profiles from a grating spectrometer are also described and the results of both methods are compared.     

Effect of reactor irradiation on the microhardness of SAV-1 and AMG-2 structural materials

The results of studying the variation in the microhardness of SAV-1 and AMG-2 aluminum alloys after irradiation with neutrons with a fluence of 10¹⁶ to 10²⁰ cm^?2 are presented. Two ranges of variation in the microhardness dependent on the indenter load are revealed, which are retained in the entire fluence range. A strong dependence of the H _μ value on P for loads less than 50 g (in the first range) is most likely caused by the physicochemical state of the surface layer.     

Densities,molar volumes,and surface tensions of Na-K-Cs ternary alloys along the two sections containing the eutectic alloy

The densities, molar volumes, and surface tensions of 21 ternary alloys of the Na-K-Cs system have been determined in the temperature range 293–453 K for the two sections directed to the Cs and K vertices and containing the eutectic alloy. The polytherms of these parameters for the Na_0.129K_0.435Cs_0.436 eutectic alloy in the temperature range 200–460 K are described by linear equations and their values at 373 K are determined to be 1406 kg m^?3, 54.62 × 10^?6 m³ mol^?1, and 77.0 mN m^?1, respectively. The isotherms of molar volumes of the ternary alloys in both sections obey the additivity rule; in the low-concentration range, cesium exhibits high surface activity.     

The Mineral Content of Rhizona cyperi after Microwave-Assisted Digestion and Determination by AAS

ABSTRACT

Rhizoma cyperi (tuberal part of Cyperus rotundus Linn) obtained from 15 different zones of China was studied to determine the contents of 16 trace elements such as 4 minor (Ca, K, Mg, and Na), 9 trace (Co, Cr, Cu, Fe, Mn, Mo, Ni, V, and Zn), and 3 toxic (Ag, Cd, and Pb) elements. The concentration determination of 16 elements was performed by atomic absorption spectrophotometry (AAS) after microwave-assisted digestion. A microwave-assisted digestion procedure based on the mixture nitric acid–hydrogen peroxide was evaluated. The method was successfully validated with the good recoveries (97–105%) against CRM GBW07603 (bush twigs and leaves). The calibration curve furnished good linear correlation coefficients (r = 0.9956–0.9999), excellent recoveries (99.35–103.7%), and limits of detection (LOD = 1–50 ng·mL^?1) suitable to determine in Rhizoma cyperi. The results showed that K, Ca, Mg, and Na were the most abundant of the major elements in Rhizoma cyperi with average concentrations of K, 26,221 µg·g^?1; Ca, 1097 µg·g^?1; Mg, 714 µg·g^?1, and Na, 293 µg·g^?1, respectively. K element was determined for the first time in this plant.     

Thermophysical properties of undercooled liquid Co-Mo alloys

Using electromagnetic levitation in combination with the oscillating drop technique and drop calorimeter method, the surface tensions and specific heats of undercooled liquid Co-10 wt% Mo, Co-26.3 wt% Mo, and Co-37.6 wt% Mo alloys were measured. The containerless state during levitation produces substantial undercoolings up to 223 K (0.13 T _L), 213 K (0.13 T _L) and 110 K (0.07 T _L) respectively for these three alloys. In their respective undercooling ranges, the surface tensions were determined to be 1895 m0.31(T m1744), 1932 m0.33(T m1682), and 1989 m0.34(T m1607) mN m^?1. According to the Butler equation, the surface tensions of these three Co-Mo alloys were also calculated, and the results agree well with the experimental data. The specific heats of these three alloys are determined to be 41.85, 43.75 and 44.92 J mol^?1 K^?1. Based on the determined surface tensions and specific heats, the changes in thermodynamics functions such as enthalpy, entropy and Gibbs free energy are predicted. Furthermore, the crystal nucleation, dendrite growth and Marangoni convection of undercooled Co-Mo alloys are investigated in the light of these measured thermophysical properties.     

Visual study of the microdrop component in sodium vapor-inert gas mixtures in a heat pipe

The parameters (size, density, and velocity) of the microdrop component in the cooling zone of a heat pipe in Na + He and Na + Kr mixtures have been determined by visualization. It is found that particles in helium have an average size of 14 μm and concentration of 1.6 × 10⁴ cm^?3, while the corresponding values for krypton are 42 μm and 3 × 10³ cm^?3. The effect of microdrops as causes of nonequilibrium enhanced concentration of sodium trimers is analyzed. Such a concentration of trimers can explain the high IR absorption coefficients (above 0.9 μm), which were previously observed in heat pipes.     

Messung der quasi-elastischen Neutronenstreuung in Glyzerin mit einem hochauflösenden Kristallspektrometer

A new neutron crystal spectrometer with an energy resolution of 6 · 10^?7 eV was installed at the Munich reactor. The high energy resolution is based on the backscattering of neutrons on silicon single crystals. The energy of the neutrons striking the glycerol sample is varied by Doppler shifting. With this spectrometer the quasielastic line broadening in glycerol was investigated at constant momentum transfer (κ=1.4 ± 0.25) Å^?1 as a function of temperature. The diffusion constants deduced from the experiment are in the order of 10^?7 cm²/s to 5 · 10^?9 cm²/s.     

Mass dependence of calcium isotope fractionations in crown-ether resin chromatography

Benzo 18-crown-6-ether resin was synthesised by the phenol condensation polymerisation process in porous silica beads, of which particle diameter was ca 60μ Calcium adsorption chromatography was performed with the synthesised resin packed in a glass column. The effluent was sampled in fractions, and the isotopic abundance ratios of ⁴²Ca, ⁴³Ca, ⁴⁴Ca, and ⁴⁸Ca against ⁴⁰Ca were measured by a thermo-ionisation mass spectrometer. The enrichment of heavier calcium isotopes was observed at the front boundary of calcium adsorption chromatogram. The mass dependence of mutual separation of calcium isotopes was analysed by using the three-isotope-plots method. The slopes of three-isotope-plots indicate the relative values of mutual separation coefficients for concerned isotopic pairs. The results have shown the normal mass dependence; isotope fractionation is proportional to the reduced mass difference, (M – M′)/MM′, where M and M′ are masses of heavy and light isotope, respectively. The mass dependence clarifies that the isotope fractionations are originated from molecular vibration. The observed separation coefficient ? is 3.1×10^?3 for the pair of ⁴⁰Ca and ⁴⁸Ca. Productivity of enriched ⁴⁸Ca by crown-ether-resin was discussed as the function of the separation coefficient and the height equivalent to the theoretical plate.     

Spectroscopic diagnostics of carbon and aluminum laser-produced plasmas

VUV emission spectra of plasmas produced by focusing laser radiation with intensity of 10¹⁰–10¹¹ W/cm² on carbon and aluminum targets were studied. Using the partial local thermodynamic equilibrium model for an electron density exceeding 10¹⁷ cm^?3, the spectroscopic diagnostics and the analysis of ion composition of plasmas were carried out. The electron temperatures determined for carbon and aluminum plasmas from the ratio of intensities of ionic lines were found to be 8±3 eV and 11±4 eV, respectively. Stark broadening of aluminum lines was measured and parameters of electron broadening were determined. Using the spatially resolved measurement of Stark line broadening, the spatial density distribution and the law of electron gas expansion were found. The electron gas in the hot region of size 5 mm with an average density of (5±2) 10₁₇cm ^?3 experienced one-dimensional expansion according to the law 1/z ^1.1 with increasing distance z from the target.     

Disintegration of metastable liquid during electrical explosion of aluminum foil

The mechanisms of disintegration of a metal melt formed during electrical explosion of aluminum foils are experimentally and theoretically investigated. The experiments were carried out on an experimental setup consisting of two current generators, one of them provided microwire explosion, while the other, an x-pinch radiograph, was used for diagnostics. In the experiments, the upper time limit of disintegration of metastable state of exploding aluminum foil was determined. For the metastable state of aluminum at internal energy of 3.5–4.5 kJ/g the calculated nucleation velocity exceeds 10¹⁴ cm^?3 · s^?1 and the critical nucleation energy is 9 ± 0.3 eV.     

X-ray structure refinement,vibrational spectroscopy,and ionic conductivity of Na0.11Ca9.64Sm0.23(PO4)6F2

The present paper is interested in the study of compounds from the apatite family, which is an apatite structure of individual rare earth substituted fluorapatite. In fact, an Sm-Bearing fluorapatite Ca_10–2yNa_ySm_y(PO₄)₆A₂ with x?=?0.11 and y?=?0.23 has been synthesized by solid-state reaction and characterized by X-ray powder diffraction. The site occupancies of substituents are 0.01091 for Sm and 0.02601 for Na in the Ca(1) position and 0.05317 for Sm in the Ca(2) position. Besides, the observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit cell group analyses and in comparison with fluorapatite and other fluorapatites. In addition to the proton conduction, the possibility of a Na⁺ contribution to the conductivity in the high-temperature phase is proposed. The highest overall conductivity values were found at σ_{475 °C}?=?2.03?×?10^?5 S cm^?1 and Ea?=?0.60 eV.     

Spontaneous emission of photons and electrons during chemisorption of chlorine on sodium

Photons and electrons are emitted when Cl₂ molecules react on a Na surface prepared by UHV evaporation. The emission yield per reacting molecule is 10^?7-10^?6 for photons and approximately 10^?5 for electrons. The dominating light emission band has a maximum at hv = 2.15 eV (width 0.6 eV). A less intense u.v. band has a maximum at about 4.7 eV. A drastic decrease in the photon and electron emission at a Cl₂ exposure of about 5.10^?3 torr·sec, is attributed to the formation of a continuous NaCl film on the Na surface.     

LED-Based Fourier Transform Spectroscopy: the HD<Superscript>16</Superscript>O Absorption Spectrum in the Range of 11200–12400 cm<Superscript>−1</Superscript>

The vibrational—rotational spectrum of the HD¹⁶O molecule is studied within the range of 11200^?12400 cm^?1. The spectrum is recorded by an IFS-125M Fourier spectrometer with a resolution of 0.05 cm^?1. The measurements are performed using a multipass White cell. A light-emitting diode is used as a radiation source. The signal-to-noise ratio was about 10⁴. The centers, intensities, and half-widths of the spectral lines are determined by fitting to the experimental data by the least-squares method. A linelist containing more than 1500 lines is created. The results obtained are compared with the experimental data of other authors.     

Raman spectroscopic study of the antimonate mineral lewisite (Ca,Fe, Na)2(Sb,Ti)2O6(O,OH)7

The mineral lewisite, (Ca, Fe, Na)₂(Sb, Ti)₂O₆(O, OH)₇, an antimony-bearing mineral, has been studied by Raman spectroscopy. A comparison is made with the Raman spectra of other minerals, including bindheimite, stibiconite, and roméite. The mineral lewisite is characterised by an intense sharp band at 517 cm^?1 with a shoulder at 507 cm^?1 assigned to SbO stretching modes. Raman bands of medium intensity for lewisite are observed at 300, 356, and 400 cm^?1. These bands are attributed to OSbO bending vibrations. Raman bands in the OH stretching region are observed at 3200, 3328, 3471 cm^?1, with a distinct shoulder at 3542 cm^?1. The latter is assigned to the stretching vibration of OH units. The first three bands are attributed to water stretching vibrations. The observation of bands in the 3200–3500 cm^?1 region suggests that water is involved in the lewisite structure. If this is the case then the formula may be better written as (Ca, Fe²⁺, Na)₂(Sb, Ti)₂(O, OH)₇ xH₂O.     

Diffusion of 22Na and 45Ca and ionic conduction in two standard soda-lime glasses

The tracer diffusivities of ²²Na and ⁴⁵Ca in two high-quality silica glasses produced by the Deutsche Glastechnische Gesellschaft as standard glasses I and II have been measured in the temperature range between 473 K and 783 K. The temperature dependences of the tracer diffusion coefficients in both glasses follow Arrhenius laws. The diffusion of ²²Na is more than six orders of magnitude faster than the diffusion of ⁴⁵Ca. The ionic conductivity was determined by frequency-dependent impedance spectroscopy and the conductivity diffusion coefficient D_σ was deduced from the dc conductivity via the Nernst–Einstein relation. The temperature dependences of D_σ for both glasses follow also Arrhenius functions. The activation parameters and pre-exponential factors for tracer diffusion and for conductivity diffusion were determined. The activation enthalpy of ²²Na and the activation enthalpy of the dc conductivity are equal, showing that the conductivity of standard glasses is due to the motion of Na ions. The viscosity diffusivities D_η were determined from available viscosity data using the Stokes–Einstein relation. They are considerably slower than both tracer diffusivities. The Haven ratios H_R are temperature independent for both glasses. The diffusivities of ²²Na and ⁴⁵Ca in soda-lime glasses increase with increasing Na₂O content.     

Microspectral analysis of dentine with femtosecond laser induced plasma

Microspectral analysis of dentine plasma produced by femtosecond laser radiation with intensities of I ～ 10¹³?10¹⁵ W/cm² in ambient atmosphere has been measured. C, O, Ca, Zn, Na, and Cu spectral lines were identified. The X-ray radiation with energies E > 30 keV has been observed upon laser beam intensities of I ～ 5 × 10¹⁵ W/cm².     

Bestimmung von Oszillatorenstärken durch Lebensdauermessungen der ersten angeregten Niveaus für die Elemente Ba,Sr, Ca,In und Na

The lifetimes of the first excited state of the elements Ca, Sr, Ba, In and Na were measured with the method ofOsberghaus ¹. Oscillator strengthes (f) of resonance lines were computed from the measured lifetimes (τ). The measurements were corrected for imprisonment of radiation in the investigated vapor. The error of the τ-values was estimated to be approximately three percent. We got following resultslifetimes for Ca 4¹ P ₁ (4·67±0·11)·10^?9sec, for Sr 5¹ p ₁ (4·56±0·21)·10^?9 sec, for Ba 6¹ p ₁ (8·36±0·25)·10^?9sec, for In 6² S _1/2 (8·531±0·085)·10^?9sec and for Na 3² P-dublett (1·59±0·039)·10^?8sec. For the Na 3² P-dublett the dependency of the lifetime on the pressure of foreign gases (N₂, C₃H₈, C₆H₅?CH₃) was studied.     

Work-hardening of Fe,Fe-0·5 wt% Si and Fe-0·9 wt% Si single crystals

Work-hardening curves of single crystals of iron and its alloys with 0·5 and 0·9 wt.% Si and paths of the tensile axis of specimens during deformation were investigated. Single crystals oriented for single glide were deformed in tension at temperatures 113, 201, 295 and 403 K at a nominal strain rate of 5·5×10^?5 sec^?1. It appears that with increasing silicon content (a) the transition between the high-temperature regime of plastic deformation (characterized by three-stage work-hardening) and the low-temperature regime is shifted to lower temperatures, (b) stage I-hardening is enhanced and (c) the flow stress level increases. These observations are explained by strong solution hardening of iron by silicon atoms which suppresses the differences between mobilities of screw and non-screw dislocations, increases the flow stress level and consequently the density of primary dislocations. As a result of this the latent hardening in the secondary slip system increases and stage I extends to a large strain.     

Doppler-limited spectra of the ν3 vibration of 12CH4 and 13CH4

The tetrahedral splittings in the P and R branches of the ν₃ band of natural methane have been examined with Doppler-limited resolution using a difference-frequency spectrometer. The spectra obtained by this difference-frequency mixer are compared to recent high-resolution grating spectrometer studies of ¹²CH₄ and enriched ¹³CH₄. The resolution, selectivity and precision are improved over the conventional methods. The mixing spectrometer utilizes tunable, narrow linewidth infrared radiation generated in the nonlinear optical crystal, LiNbO₃ as the beat frequency between a CW argon ion and a tunable dye laser. This spectrometer covers the 2.2 to 4.2 μm infrared spectrum with an instrumental resolution of 5 × 10^?4 cm^?1 and continuous scans up to ～1 cm^?1 and with ir power ～1 μW.