The chemistry of ionized acetone:Ar mixtures under varying total gas flow rate and acetone:Ar mole ratio conditions has been studied using matrix-isolation techniques. Gaseous acetone diluted in excess argon gas was subjected to electron bombardment with 300-eV electrons. The products of subsequent reaction processes were matrix isolated and analyzed by Fourier transform infrared (FTIR) absorption spectroscopy. Products included 1-propen-2-ol (the enol isomer of acetone), methane, ketene, carbon monoxide, ethane, ethene, acetylene and tricarbon monoxide. Variations in the total flow rate of gas resulted in changes in the efficiency of product formation without significant changes in the relative amounts of the major species formed. Variations in the acetone:Ar mole ratio at fixed total gas flow resulted in striking variations in the products formed, demonstrating a shift from single acetone molecule-derived charge-transfer ionization chemistry at low acetone mole ratios, to processes consistent with the participation of two or more acetone molecules at intermediate mole ratios. These results are interpreted in the context of ion-molecule reaction processes, the onset of which occurs at intermediate acetone mole ratios. Ethane dehydrogenation products are proposed to result from product secondary ionization, a process that is prevalent at high ionizing electron fluxes.

The decomposition products of the d(6) -ethane cation following charge-transfer ionization with Ar(+) , under conditions of varying ionization electron current, have been isolated in solid argon matrices at 18 K and examined using Fourier transform infrared spectroscopy. Gas samples containing 1 : 1600 d(6) -ethane : Ar were subjected to electron bombardment by using either a high (pin) or a low (plate) ionization density anode configuration with ionization currents between 20 and 150 μA. Under high ionization density conditions, the observed major products were d(4) -ethene (C(2) D(4) ) and d(2) -acetylene (C(2) D(2) ), with smaller yields of C(2) D(5) , C(2) D(3) , and C(2) D. The yield of each dehydrogenation product was enhanced with increased current. Analogous experiments employing the low ionization density plate anode resulted in reduced C(2) D(6) destruction and the formation of only C(2) D(4) and C(2) D(2) . The results suggest the onset of dissociative recombination processes under high ion density conditions. In this context, the results can be interpreted as a dissociative recombination of primary ion products, which gives rise to further dehydrogenation, and appearance of additional neutral radical products.

The products of the Ar(•+) charge exchange ionization of acetaldehyde have been isolated and compared with related photoionization results and computational work. Acetaldehyde has been used to assess the effect of varied ion density in the ionization region of the electron bombardment matrix isolation apparatus. The amount of acetaldehyde destruction has been measured for constant gas-sample composition and constant ionization current for two anode geometries: a pin anode and a plate anode. For the same ionization current, a pin-shaped anode demonstrates higher precursor molecule destruction efficiency (85%) than the plate-shaped anode (30%), resulting in substantial effect on the yield and quantity of isolated products. When the plate anode is used, the observed infrared products correspond to matrix-isolated carbon monoxide (CO), methane (CH(4)), ketene (CH(2)CO), ethynyloxy radical (HCCO), formyl radical (HCO(•)), acetyl radical (CH(3)CO(•)), vinyl alcohol (H(2)C = CH-OH), and cationic proton-bound dimer, Ar(2)H(+). When the pin anode is used, the same products are observed with different relative proportions and new absorption features corresponding to dicarbon monoxide (CCO) and methyl radical (CH(3)(•)) are observed. The surprising observation of infrared absorptions corresponding to vinyl alcohol along with low yield of products anticipated through the analysis of photoelectron-photoionization coincidence measurements suggests that the initially formed fragmentation products are able to further react within the matrix-isolation environment to influence observed product yields. Related experiments, using the isotopomer CD(3)CHO, suggest that the observed products are formed via radical-radical reactions that occur under the high pressure conditions of the matrix isolation environment.

The chemistry of ionized acetone:Ar mixtures under varied ionizing electron density conditions has been studied using matrix-isolation techniques. Gaseous acetone diluted in excess argon gas was subjected to electron bombardment with 300 eV electrons at currents between 20 and 200 μA. Linear wire 'pin' and metal 'plate' electron collector geometries were employed, allowing a wide range of electron density conditions to be explored. The products of subsequent reaction processes were matrix isolated and analyzed by Fourier transform infrared absorption spectroscopy. Products included methane, ketene, 1-propen-2-ol (the enol isomer of acetone), CO, HCO, ethane, ethane, acetylene and CCCO. Product absolute and relative yields varied with acetone number density, the choice of anode geometry and the rate of electron bombardment. The overall chemistry observed is rationalized in terms of mechanistic steps involving unimolecular cation decomposition, ion-molecule reactions, radical-radical reactions and dissociative recombination processes.