Electron-Ion Recombination Studies of Planetary Ionospheric and Astrophysical Ions.

The rates of recombination of HCO('+), H(,2)CN('+) and H(,2)CN('+)(.)HCN ions with electrons were determined as a function of electron temperature T(,e) using a microwave afterglow/mass spectrometer apparatus employing microwave electron heating. In addition, an investigation was carried out to obtain qualitatively the inelastic energy loss frequency (nu)(,(epsilon))'('inel)(T(,e)) of electrons in dilute N(,2)-Ne mixtures using microwave techniques. The recombination rate coefficient (alpha)(HCO('+)), of interest for modelling planetary ionospheres and the interstellar medium (ISM), were measured over a wide range of electron temperatures. The results of the determinations are (alpha)(HCO('+)) = (2.4 (+OR-) 0.2) x 10('-7) T(,e)(K)/300 ('-0.64(+OR-)0.05) cm('3)/sec, valid over the range 293K (LESSTHEQ) T(,e) (LESSTHEQ) 4000K and T(,+) = T(,n) = 293K. The magnitude and the temperature dependence of the recombination coefficient for this ion is similar to that predicted and measured for simple diatomic ions. The H(,2)CN('+) and H(,2)CN('+)(.)HCN ions are thought to be present in the ionospheres of the outer planets and those of their satellites, and in the ISM. Studies were carried out to obtain (alpha)(H(,2)CN('+)) and (alpha)(H(,2)CN('+)(.)HCN) values over the range 300K (LESSTHEQ) T(,e) (LESSTHEQ) 1000K and T(,+) = T(,n) = 300K, with the following results: (alpha)(H(,2)CN('+)) = (7.0 (+OR-) 1.0) x 10('-7) T(,e)(K)/300 ('-0.54(+OR-)0.05) cm('3)/sec and (alpha)(H(,2)CN('+)(.)HCN) = (3.6 (+OR-) 0.4) x 10('-6) T(,e)(K)/300 ('-0.46(+OR -)0.05) cm('3)/sec. The values are consistent with data obtained for other unclustered and clustered complex ions, respectively. Finally, qualitatively values for the inelastic energy loss frequency (nu)(,(epsilon))'('inel) was determined as a function of electron temperature for electrons colliding with N(,2) molecules in dilute N(,2)-Ne mixtures using the present microwave techniques as an alternative to the d.c. drift tube and Townsend tube methods. Our values agreed qualitatively with the (nu)(,u) values obtained by other investigators over the range 300K < T(,e) < 2000K for which our measuring technique was valid.