Heavy Molecular Ions Research Articles

Spectroscopic and thermal temperatures in the return stroke of lightning

Two different models of the temperature and state of ionization in the return stroke of a cloud-ground lightning stroke are in use in the literature. In the model that has been adopted for interpretation of the spectroscopic data on lightning, the mechanism of capture of free electrons to form negative oxygen ions is disregarded, the ionization being assumed to exist in the form of free electrons and heavy positive ions. In this case the thermalization time of the channel is expected to be short, so that the optical and thermal temperatures are effectively equal. In the model that accepts negative ion formation as a fundamental process, the ionization behind the tip of the return stroke is considered to be rapidly interchangeable between free electrons and heavy atomic and molecular oxygen ions. It is expected on this model that there exists a distinct time lag of the thermal temperature behind the optical temperature.

Dissociative recombination of electrons with molecular hydrogen ions

To a first approximation, the perturbation theory yields an explicit analytical expression for the cross section of the dissociative recombination of electrons with molecular hydrogen ions. The possible nonadiabatic transitions during the separation of the nuclei which lead to the appearance of H++H−, H(1s)+H(n=2), H(1s)+H(n=3) in finite reaction channels were considered. Numerical results are presented for the cross sections of direct and reverse reactions. The expression α=4. 2 · 10−8 T−1/2 cm3/sec2 was obtained for the recombination rate at low temperatures; this expression is in agreement with known results. Several general details of the calculation and their possible implications for the case of heavy molecular ions are discussed.

Nonradiative Dissociative Electron Capture by Molecular Ions

The rate of dissociative electron capture by heavy molecular ions is developed in the semiclassical formalism. The quantum treatment of the rate coefficient is also outlined. In the case of $\mathrm{O}_{2}^{}{}_{}{}^{+}$, $\mathrm{N}_{2}^{}{}_{}{}^{+}$, and $\mathrm{He}_{2}^{}{}_{}{}^{+}$ the calculated rate coefficients are 1.14\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$, 2.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$, and 2.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ ${\mathrm{cm}}^{3}$/sec, respectively, at 300\ifmmode^\circ\else\textdegree\fi{}K, as compared with the experimental values (1.7\ifmmode\pm\else\textpm\fi{}1)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ and (2.8\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$, and the upper limit 4.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}9}$ ${\mathrm{cm}}^{3}$/sec, respectively.