Hydrogen, chemi-ionization

The third returns the reader to chemi-ionization of cyclopropane derivatives with excited state electron acceptors. In the particular, it has been observed that oxidation of l,6-dimethylbicyclo[4.1.0]hept-3-ene (46) and [4.4.l]propella-2,6-diene (47) result in 2,6-dimethylcycloheptatriene (48) and l,6-methano[10]annulene (49) (equations 28 and 29 respectively). The former compound is conceptually the deprotonation product of the dication wherein the C-C bond between the bridgehead carbons has been totally depleted of electrons. In this case, however, the dication is not expected to be as stable as in the above pyramidal or cyclobutadiene cases and indeed, the product is seemingly not formed via the dication route. The methanoannulene likewise does not arise from the tetracation of its precursor. Rather, proton and electron transfer reactions involving merely radical cations proceed to remove hydrogens sequentially. 

Chemi-ionization of Hydrogen Atoms. Although relatively few studies have been carried out on this system, the He(2 5), He(2 5) + H reactions are of particular interest in that ab initio calculations of the forms of V, V, and W R) arc available for comparison with experimental data. The electronic states of HeH have been widely studied and the ground state has a bond energy of 2.04 eV (197 kJ mol ) and a bond length of 0.77 The calculation of the He 4- H states is... 

Attainment of equilibrium downstream of flame fronts makes it possible to use flames as media for studying high-temperature thermodynamics. Equilibrium may be approached via collisional ionization or chemi-ionization. When small concentrations of alkali metals are added to flames of low ion content, e.g., hydrogen or carbon monoxide flames, ions are produced by collisional reactions ... 

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