Appearance Potential Studies. I. Determination of Excess Kinetic Energy

Abstract

The metastable ion suppressor on the Consolidated Engineering Corporation Model 21—103 mass spectrometer has been used as a retarding potential device to determine the excess kinetic energies possessed by the ions formed during appearance potential measurements. The suppressor setting at which an ion beam is extinguished is compared with the extinction setting for an ion beam with no excess energy. These settings are studied as a function of ionizing voltage, extrapolated back to the appearance potential, and converted into units of energy. N+ from N2 was found to have no excess kinetic energy at the appearance potential. CH3+ from C2H6, CH3+ from C3H8, CN+ from C2N2, and CH3+ from C6H5CH3 were all formed with excess kinetic energy. The following quantities were deduced after taking the excess energy into account: D(CH3–CH3)=3.87 volts; D(CH3–C2H5)=3.70 volts; I(CN)=15.13 volts; I(C6H5)=9.90 volts; D(C6H5–CH3)=3.80 volts; D(C6H5–H)=4.64 volts.