A time-of-flight quadrupole mass spectrometric study of Cn+(n=1–24) ions produced by laser ablation of a graphite target

Mass spectral distributions and time-of-flight spectra of Cn+ (n=1–24) ions escaping from a carbon plasma plume generated by laser (λ=1064 nm) ablation of a graphite target are analyzed to shed light on their formation mechanisms, expansion dynamics, and laser–plume interaction. In particular, by shining the whole or a slice of the plume with a photodissociation laser (λ=266 nm) delayed with respect to the ablation laser, we examine the effects of the laser–plume interaction on the mass distribution as well as photodissociation channels of carbon-cluster cations. Also, we present experimental data that show a clear linear dependence of the velocities of Cn+ ions on 1/M. This result confirms that Cn+ ions are mainly accelerated by a transient local electric field in the plume.