Prompt and delayed dissociation of ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ induced by highly-charged-ion collisions

The prompt and delayed dissociations of ${\mathrm{N}}_2{\mathrm{O}}^{2+}\to {\mathrm{N}}^{+}+\mathrm{N}{\mathrm{O}}^{+}$ induced by electron capture collisions of 56-keV/u ${\mathrm{Ne}}^{4+}$ and ${\mathrm{Ne}}^{8+}$ ions are studied by measuring ion-pair fragments and charge-changed projectiles in triple coincidence. For the prompt dissociation, the kinetic energy release (KER) distributions are obtained and indicate this process is mainly attributed to the decay of the low-lying $1{}^3\mathrm{\Sigma }^{-}$ state ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ into ${\mathrm{N}}^{+}\left({}^{3}P\right)+{\mathrm{NO}}^{+}\left({}^1\mathrm{\Sigma }^{+}\right)$. For the delayed dissociation, since it is of difficulty to directly retrieve three-dimensional momentum vectors of ionic fragments for all the events from ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ dissociation in flight, an alternative way is proposed to only catch and analyze the events from which the ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ breakup direction is perpendicular to the time-of-flight axis. The KER distributions for these events are obtained and the metastable states of ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ are confirmed to be $1{}^3\mathrm{\Pi }$ and $2{}^3\mathrm{\Pi }$. The survival time spectra for the metastable ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ are also extracted and the mean lifetimes for the $1{}^3\mathrm{\Pi }$ and $2{}^3\mathrm{\Pi }$ conjoin, as well as the lifetimes for the identified individual metastable state, are deduced both in ${\mathrm{Ne}}^{8+}$ and ${\mathrm{Ne}}^{4+}$ collision experiments.

Figure 1

The ion-ion TOF coincidence spectra of the fragments of ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ between the first hit ion and the second one. (a) for the TI of ${\mathrm{Ne}}^{4+}$. (b) for the DC of ${\mathrm{Ne}}^{4+}$. (c) for the TI of ${\mathrm{Ne}}^{8+}$. (d) for the DC of ${\mathrm{Ne}}^{8+}$. The square solid dots in (c) represent the simulated results.

Figure 2

The KER spectra for the prompt dissociation channel ${\mathrm{N}}_2{\mathrm{O}}^{2+}\to {\mathrm{O}}^{+}+{{\mathrm{N}}_2}^{+}$. (a) for the TI of ${\mathrm{Ne}}^{4+}$. (b) for the DC of ${\mathrm{Ne}}^{4+}$. (c) for the TI of ${\mathrm{Ne}}^{8+}$. (d) for the DC of ${\mathrm{Ne}}^{8+}$. Gaussian peaks (dashed lines) are used to fit the experimental data (circular and square solid dots) and the solid lines represent the sum of their fitting.

Figure 3

The KER spectra for the prompt dissociation channel ${\mathrm{N}}_2{\mathrm{O}}^{2+}\to {\mathrm{N}}^{+}+\mathrm{N}{\mathrm{O}}^{+}$. (a) for the TI of ${\mathrm{Ne}}^{4+}$. (b) for the DC of ${\mathrm{Ne}}^{4+}$. (c) for the TI of ${\mathrm{Ne}}^{8+}$. (d) for the DC of ${\mathrm{Ne}}^{8+}$. Gaussian peaks (dashed lines) are used to fit the experimental data (circular and square solid dots) and the solid lines represent the sum of their fitting.

Figure 4

The relationship of the survival time of ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ and the TOF of ${\mathrm{N}}^{+}$ ions by numerically solving Newton's equations.

Figure 5

(a) Schematic diagram for the TOF system and the trajectory of ionic fragments from the metastable ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ dissociation perpendicular to the TOF axis. (b) The simulated relationship between the maximum distance $d_{\max }$ and the TOF of ${\mathrm{N}}^{+}$ fragment for ${\mathrm{N}}_2{\mathrm{O}}^{2+}$ dissociation in flight perpendicular to the TOF axis. (c) The relationship between the distance of ion-pair fragments hit on the detector and the TOF of ${\mathrm{N}}^{+}$ for all measured events from the delayed dissociation of ${\mathrm{N}}_2{\mathrm{O}}^{2+}\to {\mathrm{N}}^{+}+\mathrm{N}{\mathrm{O}}^{+}$ induced by the TI collision of ${\mathrm{Ne}}^{8+}$. The region labeled by the dashed line represents the events for ${\mathrm{N}}^{+}$ initially ejected perpendicular to the TOF axis.

Figure 6

The KER and lifetime spectra for the delayed dissociation of ${\mathrm{N}}_2{\mathrm{O}}^{2+}\to {\mathrm{N}}^{+}+\mathrm{N}{\mathrm{O}}^{+}$ induced by the TI collision of ${\mathrm{Ne}}^{8+}$. (a) KER distribution. (b) Survival time spectrum for selecting total KER data. (c) Survival time spectrum for A region in (a). (d) Survival time spectrum for B region in (a).

Figure 7

The KER and lifetime spectra for the delayed dissociation of ${\mathrm{N}}_2{\mathrm{O}}^{2+}\to {\mathrm{N}}^{+}+\mathrm{N}{\mathrm{O}}^{+}$ induced by the TI collision of ${\mathrm{Ne}}^{4+}$. (a) KER distribution. (b) Survival time spectrum for selecting total KER data. (c) Survival time spectrum for A region in (a). (d) Survival time spectrum for B region in (a).