Spectral analysis of the impact of ultra velocity copper spheres into copper targets

Spectrographic observations were made for copper projectiles impacting into copper targets in various controlled atmospheres. Atomic copper lines are the predominant feature of the impact flash of copper-to-copper impacts in a medium of argon. Since a copper line with a 7.1 ev excitation energy is excited in an argon atmosphere, an energy of at least this magnitude is available for excitation of copper atoms. Results indicate that in argon, the flash is produced by micron-size copper particles ejected from the target, some with velocities no less than 6-7 km/sec and heated by the medium. A collision process between copper atoms evaporated from the heated spray particles and atoms of the argon atmosphere can account for the observed copper lines. In a medium of hydrogen, the impact flash is dimmer by at least two orders of magnitude, giving a smooth spectral contour with no detectable line structure. However, no obvious black body temperature is obtainable from the contour of this light emission in hydrogen. 5516 relative velocity between copper atoms and hydrogen molecules required to produce copper lines is greater than 20 km/sec in a collision process. The reduced size of the flash in hydrogen indicates that the particles responsible for the flash are smaller than those producing the flash in argon. It appears that the size of the particles that produce the flash in each gas are of the order of magnitude of the mean free path of the molecules in that gas.