S. Bashkin

Beam Foil Spectroscopy

The methods of beam foil spectroscopy are reviewed with particular reference to the measurement of wavelengths and spectral line intensities. Photographic and photoelectric detection techniques, the methods of monitoring the beam, and doppler effects are treated in detail. Examples are given of new spectral lines which are generated with the beam foil source.

Optical spectroscopy with Van De Graaff accelerators

Abstract The utility of a beam of positive ions from a Van de Graaff accelerator for studies of optical transitions will be discussed. Particular attention will be directed to the advantages of this approach to atomic spectroscopy relative to the traditional methods.

Energy levels and mean lives of Cl II to Cl VII.

We have investigated the spectra of chlorine between 500 and 2800 A using the beam–foil technique. Over 200 multiplets have been observed, many of which had not been reported earlier. A number of such transitions could be classified and several new term values are proposed for Cl iv, Cl v, Cl vi, and Cl vii. Mean lives of various excited levels were measured for Cl ii–Cl vii. The results are compared with theoretical calculations and other measurements in appropriate isoelectronic systems.

Collisional excitation of atomic spectra in accelerated beams of light elements.

The light emitted by high-speed particles produced by a Van de Graaff accelerator and excited by passage through a thin foil of carbon has been studied in the wavelength range 2700–6600 A. Lines from deuterium, helium, nitrogen, and oxygen are presented including some that have not previously been reported. Qualitative observations are presented on the mean lives of the excited states and on the dependence of spectral line intensity upon particle energy.

Beam-Foil Studies of Nitrogen*

Beam-foil spectra of nitrogen were obtained for particle energies between 0.25 and 2.0 MeV in a wavelength range between 1050 and 3000 A and up to 5.5 MeV between 2000 and 5000 A. Most of the spectral lines are ascribed to known transitions in N i–vi. Many Si i–vi transitions could also be identified in the spectrum of the mass-28 beam. Twenty-five decay times of nitrogen were measured. In some cases, the experimental mean lives differ by factors as large as 4 from theoretical values.

Ionic Polishing of Optical Surfaces

The controlled removal of material from the surface of insulators has been observed by using a positive ion beam. In the energy range 0.5-2.0 MeV the sputtering yield was observed to be unity. The application of this technique to the manufacture of high quality optical surfaces is discussed.

Beam-foil excitation of multiply ionized nitrogen.

A detailed study is presented of the electronic excitation of a nitrogen beam accelerated by a Van de Graaff machine to energies between 0.25 and 2.0 MeV/atom, and passed through a thin carbon target foil. About 100 spectral lines of N ii through N v were detected. In addition, a number of unidentified lines were seen and their wavelengths measured. Decay times of 27 levels in N ii through N v were measured and correlated with calculated transition probabilities.

A New Method for Studying the Atom Optical spectra for multiply ionized atoms are produced by means of nuclear-physics techniques

The new spectroscopy is in its infancy, and many fascinating aspects are yet to be studied. The properties of thin films may be studied by means of the excitation they induce in a given kind of beam. The production of ions with but a single electron offers a means of carefully mapping the nuclear charge distribution without the complications introduced by the normal complement of electrons. The study of high-purity, multiply ionized particles should make for better temperature determinations in hot plasmas. Possibly the data on lifetimes and modes of decay of excited energy levels may assist in the quantitative assignment of element abundances in the stars. One can even attempt to use the glowing beams as sources for absorption spectroscopy. The method seems to permit study of every stage of excitation for every stage of ionization for every element in the periodic table. Practical problems may interfere with so complete a study, but a major extension of our knowledge of atomic structure seems to be at hand.

Beam-foil spectroscopy as of June 1970☆

Abstract The developments in beam-foil spectroscopy since 1967 will be reviewed, with particular attention given to new techniques and problems. Among the topics to be discussed are the excitation of neutral atoms, the identification of strange lines, charge identification, foil characteristics, the astrophysical application of mean-life data, and the Stark effect.

Strengths of evaporated carbon films

Abstract We have tested the capability of unsupported carbon films to separate regions at different pressures. We find that a well-mounted foil behaves as if it had the yield tensile strength of bulk graphite (5.0 × 10 8 dyn/cm 2 ), and that the median breaking strength is somewhat less than half of this value.