Kinetic-energy release inN2fragmentation by charge-changing collisions of2-MeVC+ions

Abstract

Collision-induced fragmentation of ${\mathrm{N}}_{2}$ was investigated for 2-MeV ${\mathrm{C}}^{+}$ ions under charge-changing conditions of ${\text{C}}^{+}\ensuremath{\rightarrow}{\text{C}}^{q+}$ ($q=0,2,3$). Coincidence measurement of fragment ions was performed by means of a momentum three-dimensional imaging technique at scattering angles of $\ensuremath{\theta}=0$ and $1.0$ mrad. Kinetic-energy release (KER) obtained for a fragmentation channel of ${\text{N}}_{2}^{2+}\ensuremath{\rightarrow}{\text{N}}^{+}+{\text{N}}^{+}$ was found to differ significantly in electron loss and capture collisions. In two-electron-loss collisions (${\text{C}}^{+}\ensuremath{\rightarrow}{\text{C}}^{3+}$), KER spectra were essentially identical for $\ensuremath{\theta}=0$ and $1.0$ mrad. It is concluded that the energy level of dissociating excited states of ${\mathrm{N}}_{2}^{2+}$ may be saturated when the interaction strength, defined as $\frac{q}{\mathit{vb}}$, exceeds $0.65$, where $q$ and $v$ are the charge and the velocity, respectively, of an incident ion, and $b$ is the impact parameter.