Experimental and theoretical study of the formation of germanium-carbon ion species in gaseous germane/ethene mixtures

The gas-phase chemistry of gaseous germane/ethene mixtures has been investi gated by ab initio theoretical calculations and by experiments to examine t he formation and growth of germanium-/carbon-containing species. Ion/molecu le reactions in GeH4/C2H4 mixtures have been studied with an ion trap mass spectrometer. Ion abundance variations as a function of reaction time, reac tion paths originating from primary ions of both reagents, and reaction rat e constants of the main processes have been determined. The highest yield o f new Ge-C bonds formed via reactions of Ge-containing ions with ethene mol ecules was obtained in mixtures carrying similar amounts of germane and eth ene. Reactions of GeH2.+ with ethene play a prominent role in this system. High-level theoretical methods were therefore used to determine the geometr ical structures and energies of transition structures, reaction intermediat es, and final products for several reaction pathways. Formation of the addu ct between GeH2.+ and H2C=CH2 is the initial step. This process is fairly e xothermic, and the free energy of the system allows several transformations . Isomerization pathways and H, H-2, or CH3. loss pathways starting from th is adduct have been explored. The free energy threshold defined by the firs t step shows that some transformations are likely to occur, whereas others can be regarded as inaccessible. Last, two theoretical methods have been us ed to compute the heats of formation of the attainable GeC2Hn+ species.