Collision cross-sections resonance broadening

A different approach to probe the ion-neutral potential involves the analysis of collision-broadened ion cyclotron resonance line shapes. For ions undergoing elastic collisions, the power absorption curve is Lorentzian in shape with a half-width at half-maximum equal to the collision frequency (J, which is then simply related to the reduced collision frequency, the diffusion cross section, and the ion mobility. For a series of nonreactive alkyl cations in methane, excellent agreement is found between experimental values for these quantities and theoretical values predicted from the Langevin model.H Unexpectedly, this finding may be interpreted to suggest that other mechanisms for collision broadening, namely inelastic collisions and, specifically, collisions involving complex formation, appear to be unimportant. ... 

Only collisions with Av = Av k = Av Xcos > XAvs bring the molecules out of resonance with the laser line. Collisions with An < XAvs only redistribute the velocities and do not contribute essentially to the line broadening. The cross section for these collisions with Av > XAvj is [Pg.674]

Resonance broadening collision cross in lead and mercury -sections ... 

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