Analytical and spectral features of atomic magneto-optical rotation spectroscopy (the atomic Faraday effect) of Sb,Bi, Ag and Cu with a hollow cathode lamp operated in a pulse mode

In order to increase source intensity, hollow cathode lamps were operated in a pulse mode and combined with instrumentation for Faraday or atomic magneto-optical rotation spectroscopy. The analytical and spectral features of this method were studied for the trace determination of elements Sb, Bi, Ag and Cu. Novel line crossings between the σ^±-components in the analytical line Bi I 306.772 nm were found from the dependence of the transmitted intensity on the magnetic field strength. This is related to the theoretically calculated Zeeman splitting pattern. The enhancement in the source radiance by the pulse mode gave an increase in the detection power by a factor of ten.     

Application of the atomic Faraday eftect to the trace determination of elements (Cd, Ag and Cu)—effect of the hyperfine structure on the Zeeman splitting and line-crossing

Atomic Faraday spectroscopy or atomic magneto-optical rotation spectroscopy (AMORS) combined with the electrothermal atomization was applied to the trace determination of elements (Cd, Ag and Cu). A simple theoretical treatment was developed for the dependence of the radiation transmitted through the Faraday configuration on the magnetic field strength. The effect of the hyperfine structure on the Zeeman splitting was related to the line-crossing between the Zeeman components and the dependence of the transmitted intensity on the magnetic field strength. The calibration graphs demonstrated a square-law dependence. The spectroscopic signal increased non-rectilinearly as the source radiance increased. Detection limits of 5 × 10⁻¹³, 2 × 10⁻¹¹ and 3 × 10⁻¹¹ g were obtained for Cd, Ag and Cu, respectively.     

Application of the atomic Faraday effect to the trace determination of lead

The atomic Faraday effect has been applied to the trace determination of lead in NBS Orchard Leaves, human blood, and volcanic ashes. Suspensions of powder samples and diluted whole blood are directly pipetted into a graphite tube atomizer. Spectroscopic and practical features are discussed of the atomic Faraday effect of lead. The inherent feature of insensitivity to background scattering makes the present technique suitable for practical analysis. The problem associated with loss of transmitted optical energy caused by non-atomic species was overcome by a correction method. Consequently, the present technique enabled us to perform rapid analyses, gave a detection limit of 5 × 10^?11 g and fair accuracy, at least satisfactory for practical analysis. Some problems arise from residue build-up in the atomizer.     

A novel method for atomic absorption spectroscopy based on the analyte-Zeeman effect

A new type of atomic absorption spectrometry using the Zeeman effect of sample materials is proposed. A magnetic field was applied to the sample vapor in the direction perpendicular to the propagation of light emitted from an atomic spectral source. Absorption of radiation polarized perpendicular and parallel to the magnetic field was observed alternatively. The absorption difference was proportional to the true atomic absorption, and was not interfered with by any other molecular absorption and light scattering, i.e., background absorption. The background absorption could be monitored at exactly the same wavelength as an atomic absorption line. Suitable magnetic field strength was found for each line of the various elements.     

An application of the Zeeman elect to atomic absorption spectrometry: Development of spectral-line sources stable in magnetic field

A new atomic-absorption spectrophotometer using the Zeeman effect, in which the magnetic field is applied to the light source, is described. A steady magnetic field of 3.8 kG was applied to conventional hollow-cathode lamps, which were operated using a high frequency power of 100 MHz.The π-and σ-components of the Zeeman split atomic lines were observed alternatively after traversing a flame. The absorbance difference between of the two Zeeman components was proportional to the atomic-absorption and was not influenced by background absorption. Dependences of atomic absorption signals on magnetic field strengths which were in close relation to profiles of absorption lines were measured for elements Cd, Mg, Pb, Cr, Cu and Mn by scanning of magnetic field strength.     

The contributions of magnetically induced dichroism and the resonant Voigt effect to the detection of silver by atomic spectroscopy

A simple theoretical analysis, based on the classical theory of the transmission of polarized light through a polarizing medium, has been developed to examine the factors determining the intensity of resonance radiation transmitted by a magnetized atomic vapour interposed between a pair of crossed polarizers. In common with other studies, this analysis predicts a quadratic dependence of the transmitted intensity on atom concentration but in addition, indicates that even at low atom concentrations differential absorption (dichroism) may make a significant addition to the transmitted intensity arising from differential refraction (birefringence). Further, by introducing a small angular off-set between the crossed polarizers, the concentration dependence of the transmitted intensity at low concentration may be increased and linearized. Experiments using a flame-generated atomic vapour of silver with a silver hollow cathode lamp or deuterium lamp as light source confirmed these predictions. When a strong magnetic field (9.75 kG) was used, a detection limit of 0.3 ppm (= μg/ml) for silver, with a near linear response up to 20 ppm was obtained.     

A century of progress in the sciences due to atomic weight and isotopic composition measurements

Even before the 20th century, a consistent set of internationally accepted atomic weights was an important objective of the scientific community because of the fundamental importance of these values to science, technology and trade. As the 20th century progressed, physicists, geoscientists, and metrologists collaborated with chemists to revolutionize the science of atomic weights. At the beginning of the century, atomic weights were determined from mass relationships between chemical reactants and products of known stoichiometry. They are now derived from the measured isotopic composition of elements and the atomic masses of the isotopes. Accuracy in measuring atomic weights has improved continually, leading to the revelation of small but significant variations in the isotope abundances of many elements in their normal terrestrial occurrences caused by radioactivity and a variety of physicochemical and biochemical fractionation mechanisms. This atomic-weight variability has now been recognized as providing new scientific insights into and knowledge of the history of materials. Atomic weights, except those of the monoisotopic elements, are thus no longer regarded as "constants of nature". At the beginning of the 20th century, two scales for atomic weights were in common use: that based on the atomic weight of hydrogen being 1 and that based on the atomic weight of oxygen being 16. Atomic weights are now scaled to (12)C, which has the value 12 exactly. Accurate atomic weights of silicon, silver, and argon, have enabled the values of the Avogadro, Faraday and Universal Gas constants, respectively, to be established, with consequent effects on other fundamental constants.     

Spectra of atomic Rydberg states in strong magnetic fields

Transition frequencies and intensities for exited states of atomic hydrogen in a strong magnetic field are calculated by Fourier transformation of dipole moments computed using classical trajectories. We consider states with n = 30 and L_z = 1 for fields of up to 7 T. Spectra for states labeled as librators and rotators are found to be qualitatively different, especially for the spectral component perpendicular to the field. In addition to the zero-field Kepler line, a new intra-manifold transition is located at low frequency. The frequencies and intensities are found to be sensitive functions of the field strength, and of the particular state of the Coulomb manifold involved.     

An application of the zeeman effect to analytical atomic spectroscopy-I The construction of magnetically-stable spectral sources

A design is given for a d.c. discharge lamp which will maintain a stable plasma in a magnetic field. The lamp is of particular use for applications of the Zeeman effect to analytical atomic spectroscopy. Three designs of cathode are described, which cover three different temperature ranges for the m.p. of the elements concerned. The experimental behaviour of lamps at varying magnetic field strengths, filler pressures and operating currents is considered.     

Zeeman atomic absorption spectrometry

The shift of atomic spectral lines in a magnetic field (the Zeeman effect) forms the basis for three novel developments in atomic absorption spectrometry: (i) greatly improved background correction; (ii) the use of forward scattering techniques as an analytical tool; (iii) the determination of small gaseous molecules.     

Magnetic field effects on atomic and molecular collisions

The full quantal theory of heavy-particle collisions in the presence of a static magnetic field, B, has been formulated. A new mechanism of magnetic field effect was found which depends on the velocity of the molecular center of mass and plays an important role at high-speed collisions. A power series expansion of the cross section as a function of B was obtained, which can be applied to collisions at weak field. It was also found that the differential cross section can become zero due to the magnetic field when a rovibronic energy level of a molecule is in resonance with another energy level.     

Two-beam linear magneto-optical spectroscopy of atomic transitions between short lived states

Two-beam, linear magneto-optical spectroscopy is a powerful tool for studying short-lived states. We present both measurements and a quantitative theoretical analysis of magneto-rotation observed in the forward scattering of a linearly polarised laser beam passing through an amplifying atomic medium placed in a longitudinal magnetic field. The probed transition connects two short-lived, excited atomic levels, the upper state (here the 7S _1/2 level of cesium) being prepared initially via another transition from ground state, excited by a linearly polarised pump beam. The probe polarisation undergoes three different magneto-optical processes: optical rotation, with separate contributions from the two transitions, and linear dichroism due to Hanle precession of the upper state alignment. Complete resolution of the hyperfine structures and ninety degree switching of the probe polarisation enable us to isolate all of these processes. To lowest order in optical thickness the relative intensities and lineshapes are well interpreted.     

Evaluation of a magnetically coupled microcavity hollow cathode discharge for atomic emission spectroscopy

A magnetically coupled microcavity hollow cathode discharge device was evaluated for its analytical potential as a boosted atomic emission source. A magnetic field using an electromagnet was applied perpendicular to the axis of the microcavity hollow cathode. The intensity of the atomic emission of copper, aluminum and the ionic emission of magnesium increased with increasing magnetic field until it reached a maximum. A further increase in the field strength did not lead to an enhancement of these emissions. The attainment of the maxima was attributed to the increase in the electron temperature and radial diffusion of the electrons from the center of the microcavity axis. Electron temperatures in the presence of the magnetic field calculated based on the semicorona model were shown to be proportional to the square of the reduced field strength. Further, these maxima were correlated to the energies of the upper levels of the transition studied.     

Polarized Zeeman effect atomic absorption spectrophotometry using a flame atomizer

A static magnetic field at 10 kG$\text{\$}\text{?}$was applied to a 10cm laminar flame produced by a premix type burner, and absorptions were observed for the polarized components of the radiation from a hollow cathode lamp. The dynamic range of the measurement was 10⁴–10⁵ for typical elements.The results showed that (1) the optimal conditions for double beam measurement and accurate correction of background absorption are achieved at the same time, (2) even if the flame conditions and the light intensity are changed, the baseline is not shifted, (3) the flame fluctuation noise and the lamp flicker noise are reduced, and (4) background absorption is corrected exactly at the same wavelength as the atomic absorption line.We thus concluded that the feasibility of flame atomic absorption spectrophotometry is much improved with this technique.     

An empirical chemical potential of the atomic core for non-transition element

An empirical relation between the energy of an atomic ion and its charge is determined from the experimental ionization potentials for non-transition elements. The definition of chemical potential μ_c and effective charge Z_c of the atomic core is postulated. Both are shown to be closely related to the classical electronegativity.     

Vibrational circular dichroism theory: formulation defining magnetic dipole atomic polar tensors and vibrational nuclear magnetic shielding tensors

The theory of vibrational circular dichroism is formulated in terms of magnetic dipole atomic polar tensors, an extension of infrared atomic polar tensors to magnetic dipole transitions. Relations are provided to define a vibrational nuclear magnetic shielding tensor that describes electronic shielding of an external magnetic field for a nucleus.     

Production of a spin-polarized,metastable He(23 S) beam for studies in atomic and surface physics

This beam was developed as a target for a crossed-beam electron-atom scattering experiment on the interaction of a polarized spin-1/2 electron with a polarized spin-1 atom. In the future this beam will be used in “Spin-Polarized Metastable Atom Deexcitation Spectroscopy” (SPMDS) for studying ferromagnetic surfaces without and with adsorbate layers. We use a discharge source for producing a beam of metastable helium atoms, a permanent sextupole magnet with a central stop at its exit for selecting He(2³ S) atoms in the Zeeman substatem _s =+1, a zero-field spin flipper for reversing the atomic beam polarization with respect to a magnetic guiding field, and a Stern-Gerlach magnet for analyzing the atomic polarization. At a distance of 90 cm beyond the exit of the sextupole, in the “interaction region” of an experiment, the polarized beam has a circular cross section of about 6 mm FWHM and a particle density of 1 · 10⁷ atoms/cm³. The reversible spin polarization was determined asP=0.90±0.02. A possible contamination of the beam with metastable singlet atoms is included within this value; the ground-state He atoms are not considered to be part of the polarized beam. An observed contamination with long-lived Rydberg atoms can easily be destroyed by applying a high electric field.     

Line absorption of matrix elements as a background correction error in atomic absorption spectrometry

Accurate measurement of weak atomic absorption signals is only possible after exact background correction. If the accompanying elements in excess have their own resonance lines in the immediate vicinity of the resonance line of the element to be determined,and these fall within the spectral band transmitted by the monochromator, then the value the measured apparent background absorbance is higher than the true one. The error may usually be diminished by choosing an appropriate spectral bandwidth. Tables of such bandwidths for a large number of pairs of elements are given.     

Determination of impurities in uranium compounds by atomic absorption

A method is described for the determination of 14 elements (Al, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Ni, K, Na, Zn) in uranium and uranium compounds by atomic absorption spectroscopy. A sample is dissolved in 6–8 N nitric acid, from which the uranium is selectively removed by a single extraction with tributyl phos phate. The aqueous layer is evaporated to dryness and the residue is re-dissolved in 0.2 N hydrochloric acid. Any or all of the elements can then be determined in the solution by atomic absorption spectroscopy. The limits of error in the analyses are less than 10%. Thus, the method gives about the same precision as colorimetric procedures, and it is much more precise than emission spectroscopy.