Interference Effect in Electron Emission in Heavy Ion Collisions with ${\mathrm{H}}_{\mathrm{2}}$ Detected by Comparison with the Measured Electron Spectrum from Atomic Hydrogen

Direct evidence of the interference effect in the electron emission spectra from ionization of molecular hydrogen in collisions with bare C and F ions at relatively low collision energies is presented. Oscillations due to the interference are deduced by comparing the measured double differential cross sections of the electrons emitted from molecular hydrogen to those emitted from atomic hydrogen, rather than using the calculated cross sections for H as in a previous report. We believe these experimental data provide stronger support for the evidence of the interference effect. We show that it is not only a feature of very high energy collisions, but also a feature to be observed in relatively lower energy collisions.

Figure 1

(a) The measured $e$-DDCS for $6\mathrm{MeV}/\mathrm{u}$ ${\mathrm{C}}^{6+}+{\mathrm{H}}_2$: (a) $45°$, (b) $75°$, (c) $105°$, along with the CDW-EIS predictions (solid lines). (d)–(g) Experimental-to-theoretical DDCS ratios for $45°$, $75°$, $105°$, and $150°$, respectively. The line $D_1$ in (g) is the linear fit to the data points and the dotted line ($D_2$) is to guide the eye and also indicate an oscillatory structure. The solid lines in (d)–(f) represent the fully calculated ratios, i.e., those derived using theoretical values for the DDCS for ${\mathrm{H}}_2$ and H. The peak indicated by “AI”in (f) is due to autoionization [10].

Figure 2

(a) The DDCS measured at $150°$ along with the CDW-EIS calculations (solid line) and (b) the normalized DDCS ratio ($R_N$) showing oscillation around 1, i.e., the dashed line (see text). The solid lines represent the fully calculated DDCS ratios.

Figure 3

Experimental-to-theoretical DDCS ratio $(R)$ derived using $Z_T=1.19$: (a) $45°$ and (b) $75°$ along with the theoretical-to-theoretical DDCS ratios (solid lines).

Figure 4

Fully measured DDCS ratio for ${\mathrm{F}}^{9+}$: (a) $45°$ and (b) $60°$ along with the fully calculated DDCS ratios (solid lines). The inset in (a) shows the ratios near the BE peak and that in (b) shows the DDCS for H with calculations (line). The experimental-to-theoretical ratios (dash-dotted line) are also shown for comparison.

Figure 5

The experimental-to-experimental ratios of DDCS for ${\mathrm{C}}^{6+}+{\mathrm{H}}_2/\mathrm{H}$: (a) $45°$, (b) $60°$. The arrows indicate the respective scales. The solid lines are for the fully calculated DDCS ratios.