Cluster in a Gas under Influence of an Electric Field. 935 



fig. 5 with Table II. for example, the separation of the curves 

 C and D is a measure of the disintegration of the clusters which 

 evidently is small over the region od. But for stronger fields a 

 sudden increase in the negative and positive current occurs. 

 This indicates that for electric fields of certain strength the 

 chance of a positive ion to produce a new ion by collision 

 per cm. of its path, may be greater than that of a negative 

 cluster to get broken up. This is not at all unlikely. The 

 electron attached to a molecule assumes such a position that 

 its potential energy is a minimum. This would be realized 

 to its greatest conceivable extent when the electron is sur- 

 rounded by the atoms of the molecule; and an electron getting 

 attached to a molecule would therefore tend to creep inside it. 

 To dislodge the electron the electric field would have to 

 give an amount of kinetic energy to the molecule which 

 would more or less cause it to be broken up by collision with 

 other molecules. This kinetic energy obviously need not 

 have the same value as that which must be given to a positive 

 ion to enable it to produce further ions by collision. 



The Variation of the Chance of Disintegration of an Ion. 

 Cluster with the Temperature of the Gas. 



The experiments of E. Gold and H. A. Wilson on the 

 velocity of ions in a flame show that the negative ions are in 

 the elementary state. The temperature of a flame is in the 

 neighbourhood of 1500° C, and the velocity of a molecule or 

 ion cluster is thus about 2*3 that it has at room temperature. 

 Now we have seen that the velocity that must be given by an 

 electric field to a cluster to disintegrate it at ordinary tempe- 

 ratures is much greater than 2*3 times the velocity of 

 translation. It appears, therefore, that the velocity a cluster 

 must possess in order to become disintegrated decreases with 

 increase of temperature of the gas, whether the velocity of 

 the disintegrating cluster is the result of temperature or an 

 electric field. Of course, the electric field increases the 

 temperature of a cluster through giving motion to it, but it 

 collides with molecules at a much lower temperature if the 

 gas is at room temperature. But when the disintegration is 

 due to the gas being at a high temperature, the velocity of 

 each colliding body is more or less the same. Also, in the 

 former case the ion cluster constantly loses energy by heat 

 radiation, while in the latter case it receives as much as it 

 loses. Thus the clusters may be in different states internal Iv 

 in these two cases. A change in behaviour of a cluster 

 under an electric field with rise of temperature may there- 

 fore be expected. 



3Q2 



