David S. Gough

The application of cathodic sputtering to the production of atomic vapours in atomic fluorescence spectroscopy

Abstract Cathodic sputtering is used as a source of atomic vapour for the chemical analysis of metals and alloys by atomic fluorescence spectroscopy. The sputtered vapour is produced in a Pyrex glow-discharge chamber which is suitable for the rapid interchange of flat, metallic samples. The discharge operates with a water-cooled cathode specimen and a flow-through gas control system. Linear calibration curves are obtained for the determination of nickel, chromium, copper, manganese and silicon in some iron-base alloy standards. For nickel, chromium and copper, detection limits are of the order of 20 ppm in the iron, and for manganese and silicon about 70 and 400 ppm respectively. The reproducibility of the fluorescence measurements is about ±1%. The system can be readily adapted to provide simultaneous multi-element analysis.

Perpendicularly magnetized, grooved GdTbFeCo microstructures for atom optics

Periodically grooved, micron-scale structures incorporating perpendicularly magnetized Gd10Tb6Fe80Co4 magneto-optical films have been fabricated and characterized. Such structures produce a magnetic field having flat equipotentials and whose magnitude decays exponentially with distance above the surface, making them attractive for manipulating ultracold atoms in atom optics. The GdTbFeCo films have been deposited on a Cr underlayer on a silicon (100) wafer and on a grooved silicon microstructure using DC magnetron sputtering. The films are found to have excellent magnetic properties for magnetic atom optics applications, including high remanent magnetization, high coercivity and excellent homogeneity. (Some figures in this article are in colour only in the electronic version)

Radiative lifetimes and oscillator strengths in neutral iridium

Radiative lifetimes have been determined for 25 odd-parity levels of neutral Ir using the technique of laser-excited fluorescence from sputtered metal vapour. The lifetimes are combined with branching ratio measurements to derive absolute oscillator strengths for 27 transitions in Ir I. The new lifetime values are a factor of 2.5 higher for two out of three of the only previously reported lifetimes in Ir, while the oscillator strengths are systematically smaller, by factors of up to seven, than the arc emission results of Corliss and Bozman (1962).

Radiative lifetimes in neutral platinum

Radiative lifetimes have been measured for 15 odd parity levels of neutral platinum using the technique of laser-excited fluorescence from sputtered metal vapour. The results differ significantly for two of the four levels measured previously by the beam-sputtering method. The new lifetimes for four levels are combined with the recent branching ratio data of Lotrian and Guern (1982) to derive revised transition probabilities for 15 lines and new transition probabilities for six lines.

Hyperfine structure of odd-parity levels in 91Zr I

Hyperfine structures have been investigated for odd-parity 4d25s5p and 4d35p levels for six 91Zr I transitions in the spectral range 458-549 nm using Doppler-free saturated absorption spectroscopy in a sputtered vapour. The measured hyperfine structure constants, A and B, together with results of previous studies were analysed by means of a parametric method. The interpretation was based on refined multiconfigurational fine structure calculations, which include the main Rydberg series configuration states. The analysis suggests a drastic revision of the composition of the 4d5s25p configuration levels. The main one-electron hyperfine structure parameters for the lowest configuration, i.e. 4d25s5p, are determined to be a5s10 = -2672(61) MHz, a4d01 = -115.8(3.4) MHz, a5p01 = -127.4(3.7) MHz, b4d02 = -93.5(2.8) MHz and b5p02 = -139.9(5.1) MHz. These values are in excellent agreement with ab initio calculations, justifying our choice of the perturbing configuration states.

Hyperfine structures in 51V using laser saturation spectroscopy in a hollow-cathode discharge

Doppler-free intermodulated fluorescence spectroscopy has been applied to the study of hyperfine structures in vanadium atoms sputtered in a hollow-cathode discharge. High-resolution spectra (FWHM approximately=10 MHz) which are free from background pedestals are observed. Analysis of the data yields new hyperfine-structure constants for the five 3d34s(5F)4p6D degrees levels and constants for the four 3d4(5D)4s6D metastable levels which are in agreement with recent laser-RF double-resonance results.

Hyperfine structure measurements in yttrium I using laser saturation spectroscopy in a sputtered vapour

Magnetic hyperfine interaction constants (A factors) have been determined for six excited levels, 4d5s5p z 2Do1/2, 3/2, 5/2, 7/2,and z 4Do1/2,3/2,5/2,7/2, and the two ground-term levels 4d5s2 a 2D32,5/2/ in yttrium I, using an improved method of saturated absorption spectroscopy in a sputtered vapour. The results for z 4Do12/ and z 4Do7/2 are new, while those for the other excited levels confirm recently reported A factors obtained by level-crossing optogalvanic spectroscopy and by absorption line narrowing. The measured A factors for the excited levels are compared with results of LS-coupling calculations for spd configurations.

The development of sputtering techniques and their application to atomic absorption spectrometry

Abstract The concept of using cathodic sputtering to generate atoms for chemical analysis by atomic absorption spectroscopy originated with Alan Walsh in the late 1950s. This article reviews the major developments in sputtering techniques and their application to analytical atomic absorption and fluorescence spectroscopy

Sharpening of atomic resonance lines by selective modulation

Abstract Measurements have been made of the profile of the calcium 422.67 nm resonance line detected by selective modulation, using a hollow-cathode lamp as the source and a glow-discharge sputtering cell as the modulation absorber. The observed profiles clearly demonstrate the line-narrowing associated with selective modulation, the amount of narrowing being close to that predicted for pure Doppler-broadened emission and absorption lines of equal width. Theoretical expressions are derived for the distributions of speed and direction of motion for the emitting atoms which contribute to a (sharpened) selective-modulation line.

Direct Observation of Incoherent Population Effect and Ground-State Coherence Components in Nonlinear Hanle Effect

The generation of Zeeman coherence in the lower level of a linear-σ polarized laser excited Jlower=l to Jupper=0 transition may lead to an intensity minimum in fluorescence from the upper level as an applied magnetic field is scanned through zero. The intensity variation, resulting from the coupling of the lower level coherence to the upper level population, is known as a nonabsorption resonance [1], and has a width determined by the rate at which the lower level Zeeman coherence is destroyed. A detailed theoretical treatment [2] has shown that the magnetic field dependence of the upper level fluorescence from a Doppler broadened atomic ensemble is also influenced by incoherent population transfer amongst the states of the laser excited transition that leads to a broader resonance characterized by the homogeneous transition width.