This thesis includes two parts. In the first part, a method was proposed to measure the rate constant for the formation of symmetrical proton-bound dimers at ambient pressure. The sample is continuously delivered to the drift region of an ion mobility spectrometer where it reacts with a swarm of monomer ions injected by the shutter grid. Dimer ions are formed in the drift tube and a tail appears in the ion mobility spectrum. The rate constant is derived from the mobility spectra. The proposed approach was typically examined for methyl isobutyl ketone (MIBK), 2,4-dimethyl pyridine (DMP), and dimethyl methyl phosphonate (DMMP). The proposed method was extended to measure the rate constant for the formation of protonated molecules. When the sample is continuously delivered to the drift region of the ion mobility spectrometer, it also reacts with a swarm of reactant ions injected by the shutter grid. Like dimmers, monomer ions are also formed in the drift tube and a tail appears between the reactant and monomer peaks in the spectrum. Similarly, the rate constant is derived from the mobility spectra. Some monomers appeared in the first tail, proceed to form dimmers that will appear after the monomer peak. Hence, a third tail, due to the consecutive reaction R®M®D, will appear between the reactant ion and the dimer peaks. The distribution of those dimers was calculated and subtracted from the experimental tail to obtain more accurate rate constants. In the second part of the thesis, a novel method was proposed for enhancing the separation power of ion mobility spectrometry (IMS) and other similar pulsed techniques, such as time-of-flight mass spectrometry. In this technique, rather than generating an ion packet, a dip is created in the ion beam. This is achieved by an inverse pulse applied to the shutter grid. The dip moves with the same velocity as the ion packet, and the detector reads an inverse peak at the same drift time as that of the normal operation. Using this technique, we achieved 30-60% higher resolution compared to the normal method. In addition, two close peaks that were not resolved via normal IMS were well resolved to the baseline using this technique. The main reason for the increased resolution is likely the absence of space charge in the dip.
