A Radiochemical Technique for Studying Range–energy Relationships for Heavy Ions of Kev Energies in Aluminum

A rapid technique has been developed for dissolving successive thin layers of metal from the surface of an aluminum foil: viz. electrochemical oxidation at constant voltage in aqueous ammonium citrate, followed by removal of the oxide film in a phosphoric acid – chromic oxide solution. Due to the highly protective nature of the aluminum oxide film, this two-step process enables very uniform surface layers of metal as thin as 1 μ/cm 2 to be removed. The total weight of aluminum dissolved increases with the applied anodic voltage at a rate of 0.30 μg cm −1 volt −1 (approximately 11 Å per volt) over the range 0–150 volts. The technique should be sufficiently sensitive to study the depth of penetration in aluminum of radioactive ions with kinetic energies as low as a few kiloelectron volts.An approximate value for the range of Na 24 recoil atoms from the Al 27 (n,α) reaction was obtained. A more extensive application to range studies is given in the next paper.