The dissociative ionization of nitrogen

Abstract

Energy distributions and appearance potentials of N ions produced by low-energy electron impact on N2 have been measured. At least five dissociation limits were detected either directly in the ionization efficiency curves of N or by extrapolation of the 1/2 slope straight lines drawn through the kinetic energy versus appearance potential energy diagram. Fine structure observed at low ion energy has been interpreted by the predissociation of at least two N 2 excited states one of which being the well-known C 2 Σ u + state. One of the others could be a 2 Π u state pre-dissociated to the dissociation limit at 24.34 eV. Close correlation between the results of the present work and photoelectron spectroscopic observations could be done over the electron energy range between 24.3 eV and 36 eV and assignments are discussed in detail.

The dissociative ionization of carbon monoxide

“…6. This process at 27.4 eV corresponds to dissociative autoionization as observed previously in N + from N 2 [17]. The most probable mechanism is where the CO state involved could be the 2 Π state correlated with the dissociation limit at 26.6 eV.…”

“…The energy levels of C and O + are taken from ref. (7) 29.317 C( 3 P) + O + ( 2 P 0 ) (8) 29.746 C( 1 S) + O + ( 2 D 0 ) (9) 30.736 C( 1 D) + O + ( 2 P 0 ) (10) 31.011 C( 5 P 0 ) + O + ( 4 S 0 ) (11) 32.207 C( 5 S 0 ) + O + ( 2 D 0 ) (12) 32.234 C( 1 S) + O + ( 2 P 0 ) (13) 32.430 C( 5 S 0 ) + O + ( 2 P 0 ) (14) 33.928 C( 5 P 0 ) + O + ( 2 D 0 ) (15) 35.532 C( 2 P 0 ) + O + ( 4 S 0 ) (16) 35.987 C( 5 P 0 ) + O + ( 2 P 0 ) (17) 37.226 C( 3 P) + O + ( 4 P) (18) 39.584…”

“…After the dissociative ionization study of N 2 [16] and O 2 [17], the following concluding remarks have to be extended to the dissociative ionization of CO. Even if the main limitation in the discussion of the experimental results is due to the total absence of theoretical work devoted to the CO molecule, this investigation clearly shows the major importance of two phenomena, i.e.…”

“…Unless otherwise stated, the operating conditions maintained during this work are strictly identical to those described in the previous studies of the dissociative ionization of O 2 [16] andN 2 [17]. The carbon monoxide gas, purchased from Air Liquide, is of 99.997% purity.…”

“…In N 2 + , isoelectronic with CO + , the frequently studied process [17] has been described in terms of the predissociation of the C 2 Σ u + state via accidental predissociation involving a 4 Π u bound state of N 2 + [22] or a homogeneous predissociation due to B 2 Σ + -C 2 Σ u + interaction [23]. For the dissociative ionization channel of CO + at 24.72 eV both mechanisms could account for the experimental data.…”