Collisional energy transfer and ion-molecule reaction of halomethane molecules

Abstract

Part A. Collisional Energy Transfer Quantities of Halomethane Molecules in Unimolecular Reaction of Chloroethane-1,1,2-d$_3$ The unimolecular decomposition in two-channel chloroethane-1,1,2-d$_3$ system was studied over the temperature range 663.2-763.2 K. Arrhenius parameters for this reaction were found to be: log A = $12.89\pm0.04$ and Ea = $225.82\pm{4.97}$ kJ/mol(HCl elimination); log A = $12.60\pm 0.04$ and Ea = $230.46\pm 5.17$ kJ/mol(DCl elimination). The average collision energy transferred, $<\triangle\mbox{E}>_{down}$ and $<\triangle\mbox{E}>_{all}$, were evaluated for neat system and various collider systems of $\mbox{CH_4.\; CF_4,\; CF_3H,\; CF_3Cl\; and CF_3Br}$ utilizing the stepladder model for transition probability. For these C$_1$ collider molecules, the average energies transferred were found to increase with boiling point increase and given by the expression, $<\triangle\mbox{E>_{down}(cm^{-1}) = (7.56\pm0.51) T_b(K) - (285\pm0.63)}$. These quantities were also increased with attractive potential parameter defined by the combination of polarizability with dipole moment. On the otherhand, they have shown an opposite trend on temperature effects and found to be expressed by $<\triangle\mbox{E>_{down}\propto T^{-0.7}\;\; for\;\; CH_2DCD_2Cl}$ and $<\triangle\mbox{E>_{down} \propto T^{-2.3}\;\; for\;\; CF_4}$ in the temperature range. Part B. Intracluster Ion-Molecule Reactions within CF$_3$H Cluster System Ion/molecule reactions occurring within CF$_3$H cluster ions are investigated mass spectrometrically utilizing electron impact ionization. The study of fragmentation patterns indicates that the major reactive processes are the ejection of CF$_3$ from the energized cluster ion and the formation of protonated clusters. The parentages of major fragment ions, e.g., $\mbox{(CF_3H)_nX (X = CF_2H\;\; and\;\; CF_3, n \ge 1$), are assigned from both pressure and electron energy dependence studies of these ions. The studies suggest that the precursors...