Electron-impact dissociation of $\text{CD}_3{}^{+}$ and $\text{CH}_3{}^{+}$ ions producing $\text{CD}_2{}^{+}$, ${\text{CH}}^{+}$, and ${\text{C}}^{+}$ fragment ions

Using a crossed electron-ion beams method, we measured absolute cross sections for electron-impact dissociation of the $\text{CD}_3{}^{+}$ molecular ions producing $\text{CD}_2{}^{+}$ fragment ions and $\text{CH}_3{}^{+}$ ions yielding ${\text{CH}}^{+}$ and ${\text{C}}^{+}$ fragment ions over a collision energy range from a few eV up to 100 eV. The total experimental uncertainties are about 12% at the maximum of the curves of cross sections (peak of the cross section for the ${\text{CH}}^{+}$ channel). The obtained results suggest important roles played by predissociation of bound states in the production of both the ${\text{CH}}^{+}$ and ${\text{C}}^{+}$ fragment ions. Good agreement is found with other results reported for the ${\text{CH}}^{+}$ fragment, but some differences are found for the $\text{CD}_2{}^{+}$ and ${\text{C}}^{+}$ fragments.

Figure 1

Electron-ion crossed-beams experimental apparatus. See text for an explanation. The fragment ion detector and vertical deflector are rotated $90°$ to the plane of the figure.

Figure 2

Apparent cross sections versus analyzer magnetic field measured at incident electron energy of 100 eV. The upper abscissa indicates the displacement of the signal (a) ${\text{CH}}^{+}$ and (b) ${\text{C}}^{+}$ fragments from the center of the detector by the analyzing field. The dashed vertical lines indicate the limits of our 5 mm radius detector. Solid curves represent the best fit to the data.

Figure 3

(Color online) Absolute cross sections versus interaction energy for electron-impact dissociation of $\text{CD}_3{}^{+}$ producing $\text{CD}_2{}^{+}$ fragment ions. Error bars correspond to absolute total expanded uncertainties. The solid line represents the sum of DE and DI obtained from fitting functions given in Refs. [18, 19] and the parameters given in Ref. [20]; the dashed line represents the DI contribution only.

Figure 4

(Color online) Absolute cross sections versus interaction energy for electron-impact dissociation of $\text{CH}_3{}^{+}$ producing ${\text{CH}}^{+}$ fragment ions. Error bars correspond to absolute total expanded uncertainties. The solid line represents the sum of DE and DI obtained from fitting functions given in Refs. [18, 19] and the parameters given in Ref. [20]; the dashed line represents the DI contribution only.

Figure 5

(Color online) Absolute cross sections versus interaction energy for electron-impact dissociation of $\text{CH}_3{}^{+}$ producing ${\text{C}}^{+}$ fragment ions. Error bars correspond to absolute total expanded uncertainties. The solid line represents the sum of DE and DI obtained from fitting functions given in Refs. [18, 19] and the parameters given in Ref. [20]; the dashed line represents the DI contribution only.