Delayed fragmentation of ethylene and allene induced by electron impact
Long Wei, Baihui Ren, Yu Zhang, Jiarong Wang, Bo Wang, Jie Han, Wandong Yu, Yaming Zou, Li Chen, B. Wei
Abstract
We experimentally investigated the delayed fragmentation processes of ethylene and allene dications induced by 300-eV electrons with the cold target recoil ion momentum spectroscopy in an observation window up to \ensuremath{\sim}2 \ensuremath{\mu}s. For each molecule, several distinct pathways involving prompt or delayed fragmentations were observed and relative branching ratios among them were analyzed. According to the time-of-flight coincidence measurements of corresponding recoil ionic fragments, the survival times and thus lifetimes from nanoseconds to microseconds of different delayed-dissociative precursor dications were retrieved. Besides the two-body channels, i.e., ${\mathrm{H}}^{+}+{\mathrm{C}}_{2}{{\mathrm{H}}_{3}}^{+}$ and ${\mathrm{H}}^{+}+{\mathrm{C}}_{3}{{\mathrm{H}}_{3}}^{+}$, the delayed deprotonation was also observed in many-body channels, i.e., $\mathrm{H}+{\mathrm{H}}^{+}+{\mathrm{C}}_{n}{{\mathrm{H}}_{2}}^{+}$ ($n=2$, 3) and $2\mathrm{H}/{\mathrm{H}}_{2}+{\mathrm{H}}^{+}+{\mathrm{C}}_{3}{\mathrm{H}}^{+}$. The lifetimes of the metastable intermediate diacations ${\mathrm{C}}_{n}{{\mathrm{H}}_{3}}^{2+}$ and ${\mathrm{C}}_{3}{{\mathrm{H}}_{2}}^{2+}$ were estimated.