On a Mass Spectrometric Angular Distribution Study of the Effusion of the Potassium Chloride Vapor System from Cylindrical Orifices

A mass spectrometric investigation has been made of the angular number distributions of the KCl and K₂Cl₂ molecules effusing from cylindrical orifices with geometries of $\text{L/R = 1−4}$ at temperatures of 565, 585, and 605°C. It was found that the angular distributions for neither the KCl nor the K₂Cl₂ molecule agrees with the predictions of the classical Clausing model. The angular distribution of the monomer is more diffuse than predicted by theory, whereas the dimer distribution is more highly focused than the experimental monomer distribution or the theoretical distribution. For a given orifice geometry, progressive defocusing of both beams was observed as the temperature was increased. None of the presently proposed theoretical models is capable of predicting the experimental angular distributions. However, substantial evidence exists to suggest that dissociation of the dimer on the orifice walls is an important factor.