Collision-induced emission spectroscopy of small polyatomic molecules and tandem mass spectrometry of perfluorinated organics.

Abstract

The CIE studies presented in Chapter 2 consisted of a source generated fast moving 8 keV projectile-ion, M1+•, undergoing a collision encounter with a stationary target gas, G1, under single collision conditions (i.e., ≈90%T). During the collision event, a non-momentum transfer occurs, that deposits an amount of internal excitation energy, Delta(DeltaE int), into the projectile-ion, producing an excited electronic state (M1+•)* species. Thus the (M1 +•)* species may now exhibit optical emission and/or fragment into ground, M2+ + M3•, or excited, (M2)* + M3• M2+ + (M3•) *; (M2+)* + (M3•) *, electronic state dissociation products. Additionally, if the charge exchange process between M1+• and G1 is present, a ground M1, or excited (M1)* electronic state parent neutral may be produced. Thus, again the (M1)* species may now exhibit optical emissions and/or fragment into ground or excited electronic state dissociation products. As well, with respect to the stationary target gas the (G1)* and (G1+•)* species and/or their fragments may be produced. For the small polyatomic projectile-ions studied here of the N≡N+•, C≡O+•, O=C=O +•, O=C=C=O+• systems, intact parent-ion emissions were observed for all of them, except for the latter species. As well, intact parent neutral emissions were only observed for N≡N, C≡O. For the larger polyatomic projectile-ions studied here of the C6H6+•, C6F 6+•, and C4H4O+• systems, no intact-parent emissions were observed, only those of weak atomic and diatomic fragment emissions. The tandem mass spectrometry studies of perfluorinated organics, presented in Chapters 3 and 4, were conducted on a series of iodo, oxo and unsaturated compounds. In particular, the perfluoro iodo compounds were hoped (with iodine being such a good leaving group) to be possible ideal sources of unrearranged fragment perfluorocarbocations, CnF m+. However, unfortunately this did not always prove to be the case.(e.g., the primary metastable loss from (CF3) 3CI+• was unexpectedly FI and not I• ). For the perfluoro iodo compounds, the isomers of perfluorobutyl, C4F9I, and perfluoropropyl, C3F7I, iodides were utilized as precursors. (As well, (CF3)3C--C(CF 3)3 was utilized as a precursor for (CF3) 3C+). Specifically, it was proposed here that the (fragment) perfluorocarbocations, CnFm+ possessed a reserved cation stability order (i.e., primary > secondary > tertiary); CF 3CF2CF2CF2+ > (CF 3)3CFCF2+ > (CF3) 3C+; that is not seen in their respective hydrocarbon counterparts. (Abstract shortened by UMI.)