Jean Patrick Connerade

Atomic absorption spectroscopy in the 100-600 a wavelength range.

Previous obstacles to observation of line absorption spectra in the vacuum uv below 600 A have been overcome by: (a) development of a containment device for metal vapors in a windowless system and with a negligible pressure of background gas; (b) use of a compact source of background continuum; and (c) exploitation of a normal incidence grating spectrograph which can be used with (b) to a wavelength below 300 A. As examples, the inner shell absorption spectra of Ar, Kr, Xe, Na, K, and Rb are reproduced. Slight modification of the techniques under (a) and (c) can be used when an electron synchrotron background continuum is substituted for (b).

A Study of 5p Excitation in Atomic Barium I. The 5p Absorption Spectra of Ba I, Cs I and Related Elements

New observations of the 5p spectra of Cs i and Ba i are reported. The extreme complexity of the structure does not permit precise configuration labels to be attached to all the excited levels. Nevertheless, more than 160 transitions in Ba i have been ordered into 14 series converging on experimentally known levels of the parent ion. An attempt has been made to analyse the limit structure by comparison with the data for Cs I and Hartree-Fock atomic structure calculations. The results obtained are consistent with previous interpretations of the double ionization anomaly in Ba I. Further comments are made on the comparison between experiment and the predictions of the r.p.a.e. theory for 5p excitation in Ba i. It is shown that the 5p6 6s 2S1/2-> 5p5 6s2 2P1/2 and 2P3/2 transitions of Cs i have been incorrectly identified and new assignments are proposed.

Observation of an 'Atomic Plasmon' Resonance in the Ba I Absorption Spectrum between 10 and 200 angstrom

The observation of a broad ‘atomic plasmon’ resonance, recently predicted by Wendin is reported, together with a number of discrete features due to excitation of a single electron from the 4d subshell in Ba I. HartreeFock calculations indicate mixing between configurations built on 4d9 5p6 6s2, 4d9 5p6 5d 6s and 4d9 5p6 5d2 of Ba II. Discrepancies between Wendin’s theory and experiment are attributed to this mixing. The spectrum near 16 Å arising by excitation of the 3d subshell has also been observed.

On the coupling of a Rydberg series of discrete levels to a continuum of finite bandwidth

Recent theory sheds new light on the properties of discrete levels coupled to continua of finite bandwidth. Applications of the theory to a series of resonances in the T1 I absorption spectrum are explored and some suggestions are made as to possible further extensions. Intermediate coupling calculations by using scaled Hartree–Fock parameters suggest some revision of previous assignments in the inner shell spectra of T1 I, In I and Ga I.

Observation of a 'giant resonance' in the 3p absorption spectrum of Mn i

The absorption spectrum of Mn I in the energy region corresponding to excitation of the 3p-subshell (40-70 eV) has been recorded for the first time. At least 10 discrete features are reported, as well as a broad modulation in the continuous absorption immediately above the 3p-thresholds. The spectrum is discussed in relation to previous photoabsorption data for nearby elements in the periodic table, and assignments are made by comparison with Hartree -Fock model calculations. The spectrum is dominated by a 3p-3d ‘giant resonance’.

On the simultaneous excitation of two electrons in neutral atomic zinc

In a new investigation of the Zn i absorption spectrum between 400 and 1000 Å, 11 series due to the simultaneous excitation of two electrons have been observed for the first time in Zn i. At least 120 double excitations have been measured. They are identified by comparison with published Zn ii energy levels and with Hartree-Fock calculations. The new lines may be divided broadly into two groups, a longer wavelength group (900-990 Å) due to simultaneous excitation of the two valence electrons, and a shorter wavelength group (420-610 Å) due to simultaneous excitation of one valence and one sub valence subshell electron. A detailed examination of the two groups of two-electron transitions indicates that, in both cases, excitation occurs by a final state configuration mixing process related to conjugate shake-up.

A Study of 5p Excitation in Atomic Barium: II. A Fully Relativistic Analysis of 5p Excitation in Atomic Barium

A fully relativistic ab-initio multiconfiguration Dirac-Fock (m.D.-F.) procedure has been used to identify six prominent peaks in the 5p electron-impact ionization spectrum of Bai and thereby also suggest assignments for each series limit in the 5p-photoabsorption (synchrotron radiation) spectrum of Ba I. Comparison between single configuration m.D.-F. and non-relativistic H.—F. intermediate coupling calculations show differences in the predicted ordering of levels; triple manifold m.D.-F. calculations show the interaction between configurations 5p5 6s2, 5p5 5d 6s and 5p5 5d2 of Ba II to be responsible for the prominence of supernumerary excitations in each experiment.

Inter-subshell correlations and simultaneous ejection of two photoelectrons in the absorption spectrum of Ga I

The absorption spectrum of gallium vapour between 320 and 1000 Å has been investigated for the first time; more than 90 transitions have been detected between 440 and 660 Å. The most intense of these are attributed to excitation of an electron from the 3d subshell but many features occur through simultaneous excitation of two valence electrons and derive their intensity from correlations with the single electron transitions. The concept of at 3d-core ‘hole’ in Ga I is shown to break down near the threshold for simulaneous ejection of two photoelectrons.

The Spectator Electrons Approximation in the 3d and 4s Spectra of Cr I

The 3d and 4s photoabsorption spectra of Cr I have been observed by using the synchrotron radiation emitted by the Bonn 500 MeV electron accelerator as the source of background continuum. The resulting spectrum is unexpectedly simple, and this is explained within the spectator electrons approximation. The more intense transitions can be arranged in Rydberg series. A prominent series of transmission windows arises by double excitation. A detailed analysis is presented, supported by some ab initio Hartree-Fock calculations and also by comparison with the semi-empirical calculations of Roth (1970) which include mixing between all the (3d + 4s)5 4p configurations.

Interchannel interactions and series quenching in the 5d and 6s spectra of Pb I

The absorption spectrum of lead vapour in the range 320-1070 A has been obtained. More than 60 transitions have been, found, mostly arrangable in series, which are due to excitation of either a 5d or 6s electron. Pronounced inter-channel interactions occur, similar to those in the corresponding spectrum of Tl I. Our observations confirm the applicability of a ‘ spectator model ’ for 6s excitation. The comparatively low energy of the double ionization threshold results in quenching of all but one 5d excitation series.