Optically induced transverse voltages in thin metal films

Results of experiments on laser induced voltages in metal films are summarized. The voltages are found to occur along certain directions in the plane of slant-angle vapour deposited films. A thermo-electric model based on periodic variations in the microscopic film structure, is described. The magnitude of the effect is proportional to the absorbed power/length between the contact points. Application of the films in the wavelength range 0.33–10.6μm is described and compared to more conventional detectors. A recent application, using the effect as a tool to profile non-uniformities in thin films, is also discussed.     

Accurate determination of traces of sodium and potassium in rocks by ion exchange followed by atomic absorption spectroscopy

Sodium and potassium (5–1000 p.p.m.) in rocks such as peridotites and dunites can be determined accurately by ion-exchange separation followed by atomic absorption spectrophotometry. The samples are decomposed in sulphuric, hydrochloric and hydrofluoric acid mixtures, and after removal of hydrofluoric acid the cations are absorbed on a 90-ml column of AG50W-X8 cation-exchange resin. Vanadium and other anion-forming elements are eluted with 0.01 M nitric acid containing hydrogen peroxide. Then the alkali metals are eluted with 0.50 M nitric acid, while Mg, Mn, Ca, Ti, Al, Fe and other multivalent elements are retained by the column. The eluate fractions containing the respective alkali metals are measured directly by atomic absorption spectrophotometry against standards in 0.50 M nitric acid. Relevant elution curves, results for synthetic mixtures and for three international rock standards are presented and discussed.     

Ion induced secondary electron emission from single crystal surfaces

Yields of ion impact induced electrons from very pure Ni(110) and Ni(111) surfaces have been measured. In several tilt planes the angle of incidence of a 5 keV H⁺, H⁺₂ or H⁺₃ ion beam is varied from perpendicular to grazing incidence. Below = 75° the yield increases as sec but shows characteristic depressions when the beam is incident along crystallographically low indexed lattice directions. This is explained by kinetic electron emission with respect to the projectile transparency of the crystal lattice.     

Electron density decay measurements using the 447.1 nm line of neutral helium

The 447.1 nm line of neutral helium has been used to measure the time-dependent decay of the electron density in the afterglow of a pulsed, atmospheric pressure helium discharge. The technique involves using a shutter which consists of a Pockels cell combined with crossed polarizers to gate the light pulse, allowing observation of the spectrum during various time windows in the discharge.