Investigation of ion-molecule collisions with laser-based ion mobility spectrometry

A home-built laser-based ion mobility (IM) spectrometer was employed for th e investigation of 19 aromatic compounds ranging from benzene to C-60 fulle rene. With N-2 as drift gas, the reduced mobilities K-0 obtained range from (2.51 +/- 0.03) for benz(+) to (1.02 +/- 0.05) x 10(-4) m(2) V-1 s(-1) for C-60(+). The resolution of the IM apparatus, defined as the ratio of the d rift time and the peak temporal width, was typically R = 20-50 which could be improved to R = 75 under optimal experimental conditions. A suitable mas s-mobility correlation within the hard sphere (HS) approximation was obtain ed under the assumption that the radii of the aromatic ions vary with the c ubic root of the ionic masses. Several parameters, such as diffusion coeffi cients, ionic radii and collision rate constants, were derived from the mob ility measurements.