Holmes, John L.,Mayer, Paul Michael.2009-03-252009-03-2519941994Source: Dissertation Abstracts International, Volume: 56-11, Section: B, page: 6136.9780612005440http://hdl.handle.net/10393/10414http://dx.doi.org/10.20381/ruor-16819This thesis represents the culmination of four years of research into two aspects of gas phase ion chemistry. The first was an attempt to obtain information on internal excitation in polyatomic projectile - target gas collisions in a mass spectrometer. Knowledge of internal excitation is critical to the interpretation of collision induced dissociation (CID) mass spectra. A novel collision cell was designed for a VG ZAB-2F sector mass spectrometer which permitted the detection and analysis of photon emissions from keV projectile - target gas collisions. Early experiments performed in the second field-free region of the mass spectrometer (sec. 4.2) involved the analysis of emitted light with a series of wavelength cutoff filters. Histographic emission spectra were obtained for three $\rm C\sb2,H\sb4,O\sp{+\cdot}$ ions and two $\rm C\sb2,H\sb5,Cl\sp{+\cdot}$ ions. The spectral characteristics were found to be indicative of ion structure. This led to the development of a more elaborate apparatus in the third field-free region of the ZAB which enabled the aquisition of monochromated emission spectra (sec. 4.3). The emission spectra obtained for 8 keV $\rm N\sb2\sp{+\cdot},O\sb2\sp{+\cdot}\ and\ CO\sb2\sp{+\cdot}$ projectile ions with the target gases He, N$\sb2$, O$\sb2$ and CO$\sb2$ showed that (a) collisional excitation of the ions was a vertical process, (b) considerable translational kinetic energy was converted into internal energy in the collisions (up to 22 eV) and (c) the observed emissions relate to the relative geometries of the ground and excited states of the ions. Histographic spectra for these three projectiles obtained with 18 target gasses exhibited definite trends. The abundance of fragment ions in the collision induced dissociation mass spectra of N$\sb2\sp{+\cdot}$ and CO$\sb2\sp{+\cdot}$ was found to increase linearly with emission intensity, indicating that fragmentation was the result of electronic excitation in the ions. A review was made of the degree of charge delocalization in $-$CN substituted radical cations. Semi-empirical calculations showed that the $-$CN group acted primarily as an inductive electrol withdrawing group in radical cations, carrying very little positive charge. The $-$CN group was found to raise the ionic energy of molecules compared to $-$H independent of the nature of the rest of the molecule (containing saturated, double and triple bonds or aromatic ring). The heats of formation of the $-$CN containing radical cations were 43 $\pm$ 3 kcal mol$\sp{-1}$ higher than their $-$H substituted analogues in all cases. These results were consistent with an inductive electron withdrawing cyano group which does not participate in the charge distribution of the ions. (Abstract shortened by UMI.)258 p.Chemistry, Physical.Thesis