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Chemical Reactions in the Gas Phase 

 Connected with Ionization 



MERRILL WALLEXSTEIN, AUSTIN L. WAHRHAFTIG, 

 HENRY ROSENSTOCK, AND HENRY EYRING 



Department of Chemistry 



University of Utah 



Salt Lake City, Utah 



The previous papers in this symposium have dealt with the physical 

 theory basic to the study of the interaction of high-velocity particles 

 with matter. We wish to take the first step toward the consideration of 

 complex systems, to consider processes sufficiently simple so that the 

 application of approximate quantum mechanical and statistical calcula- 

 tions is possible, yet sufficiently complex to point the way toward a 

 correct discussion of systems of biological interest. Thus, this report 

 will deal largely with the effect of bombardment of isolated molecules 

 by electrons, under such conditions that no secondary reactions occur 

 between the products of the bombardment. 



Most of the subsequent discussion will be based upon data obtained 

 with a mass spectrometer. Let us consider just what information can 

 be so obtained. Almost all the mass spectrometric data now available 

 have been obtained with instruments of the Dempster-Nier type. Here 

 the substance to be studied, which must have a vapor pressure of at 

 least a millimeter or so at a reasonable temperature, is introduced into 

 the ionization region through a capillary leak to give a pressure of about 

 10~* mm. It is there bombarded by a beam of electrons of known energy, 

 commonly variable over the range 0-100 volts, and the positive ions 

 formed are accelerated by a small field, a few volts per centimeter, 

 toward a slit. Those that pass through are accelerated by a "high 

 potential" of 300-5000 volts and focussed on a second slit, the entrance 

 slit to the analyzer section. Depending upon the type of instrument, 

 180, 90, or 60°, the ions diverging from the entrance slit pass through a 

 magnetic field in which they follow circular paths of radius 



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