J. A. Kernahan

Beam-Foil Lifetime Measurements Using ANDC Analysis for the Resonance Doublet in Ar VIII, Kr VIII and Xe VIII

Some practical methods are suggested for applying the Arbitrarily Normalized Decay Curve (ANDC) method for cascade-correction in beam-foil lifetime measurements. These methods are used to analyze decay curves recorded for the ns2S-np2P0 resonance doublet in Ar VIII, Kr VIII and Xe VIII by including the np2P0-nd2D cascade transitions in the analysis. The f-values derived from the np lifetimes for the ns-sp multiplet are in good agreement with recent theoretical estimates for Ar VIII and Kr VIII and agree with theory for Xe VIII within the combined experimental and theoretical uncertainties.

Study of the beam-foil spectrum of Xe vi, and Xe vii, and Xe viii from 500 to 1550 Å

A survey has been made of the beam-foil spectrum of xenon between 500 and 1550 A at an energy of 1.6 MeV. Mean lives have been obtained from 18 lines, all but five of which have been classified as Xe vi, Xe vii, or Xe viii lines. Our proposed classifications for two lines would enable the 4f, 5g, and 6g terms in Xe viii to be connected to the rest of the system. Along the In i isoelectronic sequence, the oscillator strength of the 5s25p2Po−5s25d2D transition is compared with previous theory and experiment, and the wavelengths of the I v transitions in this sequence are proposed.

Beam-foil Studies of Phosphorus in the Vacuum Ultraviolet

We have measured lifetimes for 24 terms in P I-P V using the beam-foil technique in the vacuum UV region. The results have been compared with theoretical calculations and with other experimental values. Several significant discrepancies with earlier results have been found. We present the first experimental lifetimes for 9 terms. Most of our lifetimes can be converted directly into f-values, and we discuss these in relation to trends along isoelectronic sequences. Configuration interaction is found to be important for several transitions. We also suggest a revision of the recently-determined abundance of phosphorus in interstellar clouds, based upon our new f-value for the 1 308 ? multiplet in P II.

Mean-life Measurements for Levels in BI-BIV

We have studied beam-foil spectra of boron in the wavelength range 385 ? to 5 000 ?, and measured mean lives for 35 levels in B I-B IV. Where possible, we have deduced experimental oscillator strengths for the transitions studied, and we compare our results with other work both theoretical and experimental.

Beam-foil mean-life measurements in krypton

Foil excitation of a beam of ionized krypton has yielded spectra in the wavelength range 434–1236 A for incident ion energies in the range 0.3–1.8 MeV. Radiative mean-life measurements have been performed using 32 transitions in Kr i-Kr viii. For several Kr vii and Kr viii transitions we have converted our mean-life results into absorption oscillator strengths for comparison with values suggested by Sorensen and co-workers by extrapolation along isoelectronic sequences.

Radiative Lifetime Measurements in Al II-VII

We have used the beam-foil technique to study spectra of aluminium in the wavelength range 300 A to 2000 A, and measured radiative mean lives for 22 levels in Al II-Al VII. Where possible, our results are compared with theory and other experimental work.

Energies and lifetimes of excited atomic states in Ar v–Ar viii

The spectra of Ar v–Ar viii have been studied in the wavelength region of 400–1500 A by using beam-foil excitation. Several new transition classifications are proposed in Ar vii and Ar viii. Lifetimes have been measured for 19 excited states in Ar v–Ar viii. The results are compared with previous measurements and with theoretical calculations.

Beam-foil spectroscopy of the Cu I and Zn I isoelectronic sequences☆

Abstract A summary is presented of recent investigations of the Cu I and Zn I isoelectronic sequences. A discussion is given of the 4s4d 1D term, with a provisional energy assignment being made for Se V. Two other Se V terms and five As V terms are also assigned. Lifetimes are presented for the 4p, 4d and 5s levels of the Ge IV, As V and Se VI members of the Cu I sequence, the 4p results being obtained from ANDC analyses using decay curve data the 4s-4p, 4p-5s and 4p-4d transitions. The multiplet ƒ-values derived for the 4s-4p transition are in excellent agreement with theoretical predictions. Lifetimes are also given for the 4s4p 1P0, 4p2 1D2, 4s4d 1D2 and 4s5s 1S0 levels of the Ge III, AS IV and Se V members of the Zn I sequence, the 4s4p 1P0 results again coming from ANDC or constrained-fitting analyses. The agreement with theoretical values here is good up to As IV, but for higher series members the theoretical ƒ-values are significantly higher than the experimental values. Possible reasons for this discrepancy are discussed.

Beam-foil spectroscopy of bromine from 450 to 1000 Å

Beam-foil excitation of the bromine spectrum has been applied to the measurement of radiative lifetimes for eight terms in Br v to Br vii, using HBr+ ions of energy 0.5–1.6 MeV. The multiplet f values derived from these results are found to be reasonably consistent with other measurements for the analogous transitions in homologous atoms, except for the 4s4p2 2D term in Br v, where configuration interaction is known to be important. Agreement within a factor of two is found with f values forecast by calculations based upon the Coulomb approximation. The behavior of the f values of the 4s2 1S–4s4p1P0 and 4s4p3P0–4s4d3D transitions along the Zn i isoelectronic sequence is considered in detail, and again the experimental results are consistent with each other but differ from f values calculated by several techniques by a factor of about two. Many previously unclassified lines have been observed, and tentative assignments are suggested for five of these. Decay curves have also been recorded for nine spectral features in the region 550–650 A, which suggest that the 1P0, 1D0, 3P0, and 3D0 terms of the 4p4d configuration in Br iv all have lifetimes in the range 0.08–0.14 ns.

Energy-level and lifetime measurements for Sb IV and Sb V

A study of the beam-foil spectrum produced by a 1-MeV beam of antimony ions has yielded lifetimes for nine lowlying terms of Sb iv and six of Sb v. Decay-curve analysis incorporating the andc method to correct for cascade effects has given lifetimes for the upper state involved in the resonance transitions of both ions that are in reasonable agreement with most recent calculations. New energy-level assignments are given for the 5s5d1D2, 5s6d1D2, and 5s4f1F3 levels of Sb iv and for the 6d2D3/2,5/2 and 4f2F5/2,7/2 levels of Sb v.