Stopping power measurements for low energy ions in gases by time-of-flight spectroscopy

Abstract

In the nuclear stopping regime, measurements of the specific energy loss imply strong requirements on the applied projectiles, targets and particle spectrometers. It is shown in detail that the high experimental demands can be fulfilled by using ion beams from an electromagnetic isotope separator, gas targets and the time-of-flight technique. Systematic energy loss measurements were performed at the Bonn mass separator with singly charged ions of the 5p-, 6s- and 4f-elements at energies between 10 and 90 keV, with hydrogen as stopper gas at pressures between 0 and 0.2 mbar and with a time-of-flight spectrometer of the pulsed beam deflection type. 35 different stopping power values are derived and compared with corresponding atomic size parameters. The observed 20% shell effect of the elastic stopping cross section (“Z 1 oscillation”) is in agreement with previous range and sputtering results.