Emission of Secondary Electrons from Nickel and Molybdenum by Neutral Atoms of Mercury and Potassium

Investigations have been carried out on the emission of secondary electrons from N 1 and Mo produced by high speed neutral atoms of mercury and potassium. The mercury particles were produced by neutralizing a homogeneous beam of accelerated ions from a hot-cathode mercury arc on the walls of a narrow nickel canal which they strike at grazing incidence. The neutral atoms of potassium were produced by passing a beam of fast ions of definite velocities through vapours of potassium where they are neutralized by electron exchange with neutral K atoms. It is observed that the secondary emission rises with the number and the energy of the particles and that the energy distribution among the secondary electrons is always Maxwellian, suggesting that the emission is probably due to intense local heating. The effective temperatures of the target have been calculated in typical conditions. It is also shown that the targets scatter neutral atoms, dirty surfaces scatter more Hg atoms than clean ones but the reverse is the case with K particles.