Paul D. Zemany

Effect of Various Gases on Potassium Ion Emission from Hot Platinum

The effect of several gases on the emission of potassium ions from a hot platinum surface has been studied. It has been found that oxygen, carbon tetrachloride, bromine, and helium cause a marked decrease in the potassium emission; nitrogen has a smaller effect; and hydrogen causes an increase in the emission.

Free Molecular Flow in the Sample Inlet to the Mass Spectrometer

The aspects of free molecular flow in the sample inlet to the mass spectrometer are pointed out and the conditions under which such flow can occur are described. Methods for calculating the leak diameter and sample pressure for various flow rates are developed. These principles are illustrated by consideration of the flow characteristics in the mass spectrometer leak detector, and by an example from reaction kinetic studies.The decrease in pressure in the sample reservoir is also described. This is applied to a determination of molecular weights. The effect of the pressure decrease on apparent fragmentation patterns is pointed out and a rational expression for spectrometer sensitivity is suggested which is based on the fraction of molecules which flow through the spectrometer which appear as ions.

Molecular Weight Determinations by Effusiometry

An effusiometer using a thermistor as a pressure gauge is described. Molecular weights can be determined with it with an average error of ±2 percent. Only a few hundredths of a cubic centimeter of gas at N.T.P. is required as a sample, and may be recovered.