Molecular enhancement of Balmer emissions following foil-induced dissociation of fastH2+andH3+ions

Abstract

Relative emission yields of Balmer lines as functions of the dwell time (${t}_{D}=0.97\ensuremath{-}54.1$ fs) in thin carbon foils (2-68 \ensuremath{\mu} g/${\mathrm{cm}}^{2}$) have been measured with (0.2-0.8)-MeV/amu ${\mathrm{H}}^{+}$, ${\mathrm{H}}_{2}^{+}$, and ${\mathrm{H}}_{3}^{+}$ incident on thin carbon foils. Large molecular effects for emission yields of Balmer lines have been observed for ${\mathrm{H}}_{2}^{+}$ and ${\mathrm{H}}_{3}^{+}$, where the molecular effect for ${\mathrm{H}}_{3}^{+}$ is larger than that for ${\mathrm{H}}_{2}^{+}$. The molecular effects for ${\mathrm{H}}_{2}^{+}$ and ${\mathrm{H}}_{3}^{+}$ depend on the principal quantum number ($n=3\ensuremath{-}6$), but this $n$ dependence disappears at the largest ${t}_{D} (=54.1$ fs). The molecular effects rapidly decrease with increasing ${t}_{D}$ in the small-${t}_{D} (\ensuremath{\lesssim}2$ fs) region and more slowly decrease in the large-${t}_{D} (\ensuremath{\gtrsim}2$ fs) region. The magnitudes of the molecular effects at the largest ${t}_{D} (=54.1$ fs) are in good agreement with those by Andresen et al. [Phys. Scr. 19, 335 (1979)]. Relative populations of $n$-state hydrogens in the large-${t}_{D} (\ensuremath{\gtrsim}2$ fs) region have been derived from the relative yields of Balmer lines as functions of $n$ and ${t}_{D}$. The molecular enhancement for relative populations of $n$-state hydrogens for ${\mathrm{H}}_{2}^{+}$ depends on $n$ and ${t}_{D}$, and decreases with increasing ${t}_{D}$ and increases with increasing $n$. Some discussions are presented on the mechanism of production of excited $\mathrm{H}(n)$ atoms from incident ${\mathrm{H}}^{+}$ and of $\mathrm{H}(n)+{\mathrm{H}}^{+}$ or ${2\mathrm{H}}^{+}$ breakup fragments from incident ${\mathrm{H}}_{2}^{+}$ (${\mathrm{H}}_{3}^{+}$).