Stereodynamic studies of intracluster ion-molecule and radical-molecule reactions

Abstract

Intracluster Ion-Molecule Reactions of Methane Homocluster : The ion-molecule reactions within ionized methane clusters are investigated utilizing an electron-impact mass spectrometry. A number of ionic reaction products are observed and interpreted as series of cluster ions of the form $(CH_4)_n X^{+}$ where X = $CH_4, CH_5, C_2 H_2, C_2 H_3, C_2 H_4, C_2 H_5, C_2 H_6$ and $C_2 H_7$, and n>0. These cluster series, except for $X = C_2 H_7$ and $C_2 H_6$, are interpreted in terms of known bimolecular ionic reactions as both electron impact energy and pressure dependencies. The two cluster ions with $X = C_2 H_7$ and $C_2 H_6$ demonstrate cluster reactions occurring easily in a solvated environment. Meanwhile, the $C_3 H_3^{+} and C_3 H_5^{+}$ ions show evidence of consecutive ionic reactions. Possible reaction paths are discussed and compared with previous works using photoionization of methane clusters and high pressure mass spectrometry. Reactions of Ground State Oxygen Atoms with CFCl=CXY (X,Y=H, F, Cl): Effect of Steric Hindrance and Direct Cleavage of Double Bond : The reactions of $O(^{3}P)$ with CFCl=CXY (X, Y = H, F, Cl) have been studied via chemiluminescence image technique under discharge flow conditions. The concentration profile of the $O(^{3}P)$ atom during reaction has been monitored using $NO_2$ chemiluminescence imaging from the entire reaction zone by a charge-coupled device camera. The observed rate coefficients of $O(^{3}P)$ with $CH_2=CH_2, CFCl=CF_2, CFCl=CH_2, CFCl=CFCl, CFCl=CHCl$, and $CFCl=CCl_2$ at room temperature are 7.38, 5.04, 4.43, 2.67, 1.57, and $1.36 \times 10^{-13} cm^{3} molecule^{-1} s^{-1}$, respectively. The reaction behaviors have been interpreted in terms of steric hindrance of chlorine atom and change of reaction mechanism to a direct C=C bond cleavage by fluorine atoms.