Mechanism of collisional heating in electrospray mass spectrometry: Ion trajectory calculations

To simulate the multicollisional heating process taking place in the interm ediate pressure region of an electrospray source, ion trajectory calculatio ns have been performed by introducing in the SIMION program a subroutine fo r handling the collision dynamics. The simulated internal energy distributi ons are compared with already available experimental distributions obtained by the "survival ion yield" method (Collette, C.; Drahos, L.; De Pauw, E.; Vekey, K. Rapid Commun. Mass Spectrom. 1998, 12, 1673). The latter have be en satisfactorily reproduced by using a statistical model for the energy re distribution between the ion and the target gas. This model takes into acco unt both activation and deactivation processes occurring upon collision in the acceleration/fragmentation region. It accounts for the important role o f the number of degrees of freedom of the target on the shape of the intern al energy distribution.