A computer simulation study of ion-molecule reactions in the mass spectrometer

Relative ion abundances were calculated on the basis of a collision model for multiple order ion-molecule reactions. Allowance was made for the energy dependency of reaction cross sections and the existence of long-lived intermediates whose dissociation was assumed to follow unimolecular decay kinetics. Cross section and rate constant values severely affected calculated abundance curves and permitted the assignment of reaction mechanisms. The model was applied to the ethylene system under conditions where only one primary ion, C[lowered 2]H[lowered 4, raised +], was present, pressures varied from zero to ~0.03 Torr, ion paths were relatively long (0.54 cm), and drawout fields were low (