1092 



distance and it seems extremely useful for the precise determination 

 of the ionisation tension. Tliis method has the advantage that it is 

 quite independent of eventually existing conlact potentials and 

 besides, that it does not only determine the ionisation tension itself 

 but also a series of multiples of il, so that the mean value can 

 exactly be calculated. 



STRDOM 



150 



100 



50 



Fig. 3 



4. Hkrtz ') concluded from the experiment made by him together 



with Franck on helium, that the energy transmitted by an electron 



to a helium atom at a non-ionising impact has just the value it 



would have when the impact took place between perfectly elastic 



•spheres with the mass of the electron resp. of the helium atom. 



Let us suppose now, that also in the argon the impact between an 



electron and an argon atom follows the law of the elastic impulse. 



We then find that during a non-ionising impact the electron loses a 



quantity of energy equal to ]^r=zkE, where /i" represents the energy 



of the electron and k a constant, equal to double the quotient of 



the mass of the electron by that of the argon atom : 



Wg 2 



/t — 2 — — — = 0,000027. 



ma 1844.40 



Now we can also calculate the increase of the energy of the 



1) Verb. D. phys. Ges. (19) 268 1917 Verg. Benade Phys. Rev. (10) '.: 1917. 



