Electron impact ionization of and : contributions from different dissociation channels of multiply ionized molecules

Abstract

The cross sections of ionic products due to the electron impact ionization of N 2 and O 2 have been measured for the electron energies from threshold up to 600 eV. The contributions to the cross sections from the possible reaction channels after the multiple ionization of molecules are also determined. The experiment shows that for both N 2 and O 2 the singly charged fragment N + or O + originates mainly (∼70%) from the contribution of the dissociation of the singly charged parent ions, whereas the doubly charged fragments N 2+ or O 2+ are mainly (∼70%) from the dissociation channel of doubly ionized N 2 into N 2+ + N or O 2 into O 2+ + O, respectively. At high electron energies, 85% of singly ionized N 2 molecules stabilize into N + 2 , whereas about 70% of singly ionized O 2 molecules stabilize into O + 2 . More than 80% of doubly ionized N 2 and O 2 molecules dissociate through the equal charge separation channel. However, after triple ionization, most of the molecules dissociate into two charged fragments. The experiment also shows that the total cross sections for the different ionization stages decrease exponentially as the ionization stage increases.

CRITICAL REVIEW OF N, N + , N + 2 , N ++ , And N ++ 2 MAIN PRODUCTION PROCESSES AND REACTIONS OF RELEVANCE TO TITAN'S ATMOSPHERE

“…Shaw (1992) measured the absolute absorption cross section and the photoionization quantum efficiency from threshold up to 25.6 eV. The N + 2 formation cross section by electron impact has been measured by Tian & Vidal (1998), from threshold up to 600 eV (see the comment of Stebbings & Lindsay (2001) on the accuracy of these cross sections). The N + 2 formation cross section is a maximum (∼1.85 × 10 −16 cm 2 ) for an electron energy of 80-100 eV (Itikawa 2006 (X, v = 1-4) states are also populated, both by autoionization in the case of photoionization and by radiative cascades from excited electronic states.…”

“…Above the double ionization threshold at 42.88 eV, there is a small contribution from N ++ 2 doubly charged ions, which have the same mass-tocharge ratio (m/z) as N + fragment ions. Tian & Vidal (1998) measured the N 2 electron impact ionization cross sections to form N + 2 , N + , and N ++ 2 ions from threshold up to 600 eV electron energy. They found that the N + production cross section reaches a maximum value of 6.6 × 10 −17 cm 2 at 120 eV electron energy (see the review from Itikawa 2006).…”

Suprathermal electron spectra in the Venus ionosphere

“…For the electronic excitation of atomic species, we adopt the cross sections of Stone et al [2002] for H and He, Laher and Gilmore [1990] for O, Goembel [1991, 1992] and Yang and Doering [1996] for N. For electron impact ionization, the cross sections of Bartlett and Stelbovics [2004] are used for H, He and N, and those of Laher and Gilmore [1990] are used for O. For N 2 , the dissociative ionization cross sections are taken from Tian and Vidal [1998b] and Shemansky and Liu [2005], while those for vibrational and electronic excitations from Itikawa [2006]. An additional process of neutral dissociation (N+N) is considered in our calculations, with the cross-section data taken from Cosby [1993].…”

Runaway of electrons in dense gases and mechanism of generation of high-power subnanosecond beams

“…2-4) are based on data [8,[36][37][38][39][40][41][42]. Total cross-sections of an electron -a nitrogen molecule collision were collected from [43][44][45][46][47] and cross sections of nitrogen molecule ionization from [48][49][50][51]. The excitation of 10 the lowest electronic states (data of [52,53]) and the 8 lowest vibration levels ( [54,55]) of a nitrogen molecule were accounted (Fig.…”