R M Lowe

Determination of atomic lifetimes using pulsed laser excitation of sputtered metal vapours

A lifetime method based on measuring the fluorescence decay following pulsed laser excitation of sputtered metal vapours is described. The method is applicable to neutral and singly ionised atoms of a wide range of elements, including the highly refractory metals. New lifetime results are reported for some levels of Zr I and Zr II.

Radiative lifetimes and branching ratios for the 62P0 levels of gold

Measurements have been made of the radiative lifetimes of the 62P32/0 and 62P12/0 levels of neutral gold and of the branching ratios of the five transitions originating from these levels. The lifetimes were determined by measuring the fluorescence decay following pulsed laser excitation of gold vapour produced by cathodic sputtering in a rare-gas discharge. The lifetime and branching ratio results are combined to derive absolute f values for the 2428 and 2676 AA principal resonance lines and also for the 3123, 5065 and 6278 AA lines. The new f value for the 3123 AA line is used together with the solar data of Ross and Aller (1972) to obtain a revised value of the gold solar abundance.

Radiative lifetimes of low-lying levels in Sm I

The radiative lifetimes of 26 low-lying 4f66s6p levels of Sm I have been determined from measurements of time-resolved laser-induced fluorescence. The measured lifetimes for four of the levels are in agreement with previous work; however the results for the 17811 cm-1 7F00 and 17770 cm-1 7F10 levels are longer than previously reported values by factors of 50 and 4, respectively.

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.

New atomic lifetime results for some levels of neutral yttrium

Radiative lifetimes have been determined for the z2D degrees 3/2,5/2, z2F degrees 5/2,7/2, y2D degrees 3/2, 5/2, y2P degrees 3/2 and y2F degrees 5/2, 7/2 levels of neutral yttrium using the newly established technique of laser excited fluorescence from sputtered metal vapours. The results differ significantly from previously reported values obtained by the Hanle and level-crossing techniques (1970, 1971) and by beam-foil and beam-sputtering techniques, but they are consistent with relative lifetime values derived from the recent hook data of Cardon and co-workers (1980). The new lifetime results are used to determine a revised normalisation factor for the conversion of Cardons relative f values into absolute values.

Abnormal broadening of boron emission lines in glow-discharge lamps: evidence for excitation in low-energy B-Ar(Kr or Xe) collisions

The profiles of the boron resonance lines emitted from hollow-cathode and planar-cathode glow-discharge lamps have been studied for a variety of discharge conditions. For discharges operated in argon, krypton or xenon, the lines are extremely broad (halfwidths 0.13-0.27 AA) and are emitted very close to the cathode surface with unusually high intensity. The abnormal linewidths are due to Doppler broadening, which is unusually large because of a preferred excitation for those sputtered boron atoms possessing high kinetic energies of ejection. Investigations of the excitation process suggest that the energetic boron atoms are excited by inelastic collisions with rare-gas atoms. The high excitation efficiency at relatively low collision energies is interpreted in terms of curve crossings, which appear to be particularly favourable for some boron-rare-gas systems.

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.

Radiative lifetimes in Mo II

Atomic lifetimes have been determined for fifteen levels of the z6F0, z4P0, z6P0 and z6D0 terms of Mo II, using the technique of laser-induced fluorescence from sputtered metal vapour. The new lifetime results allow relative Mo II oscillator strengths reported recently by Schnehage et al. (1983) to be placed on an absolute scale.

Radiative lifetimes in Fe II using selective laser excitation

Radiative lifetimes have been determined for thirteen levels in Fe II using the technique of laser-excited fluorescence from sputtered metal vapour. Results for the quartet terms, z4P0, z4D0 and z4F0, are new, while those for the z6D0 term are in agreement with the results of previous electron excitation experiments.