Relative partial ionization cross sections of N2O under 10–25-keV electron impact

Abstract

The relative partial ionization cross sections for the fragment ions produced in direct and dissociative ionization of a N 2 O molecule are measured for impact of 10-25-keV electrons by using an electron-ion-coincidence technique with a linear time-of-flight spectrometer. The six ionic fragments of N 2 O (N 2 O + , NO + , N 2 + , O + , N + , and N 2+ + O 2+ ) are observed and identified. The impact energy dependence of the partial ionization cross sections for these ions is expressed relative to the cross section of N 2 O + and is found to be nearly invariant. The relative ionic fractions for the produced ions of N 2 O are also obtained and compared with the earlier reported data available at lower energies of electron impact. It is found that the relative ionic fractions for singly charged fragments are almost energy independent. However, for the doubly charged fragment ions (N 2+ + O 2+ ), the present data are found to be higher by almost a factor of four compared to the relative ionic fraction reported earlier at a very low impact energy.

Fragmentation ofCO22+in collisions with low-energy electrons

“…These islands are in good agreement with previous studies by Bhatt et al for an electron energy of 12 keV [4]. However there are also some differences.…”

“…This can be easily explained with the Coulomb explosion picture, since the distance between the two oxygen atoms is larger than that between carbon and oxygen due to the linear configuration, the KER of the channel C+ + 0+ + O should be correspondingly large. As mentioned above, this is just the opposite in [4]; in their case of 12 keV electron impact, the KER distribution for the 0 + + 0 + + C channel is narrower than that for the C+ + 0+ + O channel. This sug gests that at high electron energies, higher electronic states are involved, which might cause the failure of Coulomb explosion picture.…”

“…[4], where they argued that it originates from a predominant contribution from the initial charge separation of the sequential process [Two-step(i)2 in Table I] with a mixture of contributions from the concerted mechanism.…”

“…Moreover, there is a scenario in between these two above, the asynchronous breakup, in which the bonds break in a single step but at a time where the vibration and rotation processes precede the fragmentation. Although numerous studies have been performed to investigate the breakup mechanism for C 0 22+ and C 0 23+ [1,3,5,6,12] with ions and laser as perturbation, the electron-impact ionization of C 0 2 and its subsequent dissociation mechanisms studies under impact energies are scarce in the available literature [4,[18][19][20]33], In the present work, a cold target recoil ion momentum spectroscopy(COLTRIMS) was adopted to study the fragmentation of C 0 22+ formed in low energy electron induced ionization of C 0 2. By measuring the momentum vectors of the fragment ions in coincidence, the KER distributions and the slopes in the two-dimensional ion-ion coincidence map for different dissociation channels were obtained.…”

“…Various projectiles have been applied to generate numerous molecular ions, including synchrotron radiation [6][7][8][9][10], positively and negatively charged ions [2,5,[11][12][13][14][15][16], electrons [4,[17][18][19][20][21], and intense lasers [3,[22][23][24][25][26][27][28][29][30].…”