Fragmentation of and electron detachment from hot copper and silver dimer anions: A comparison

We measured the spontaneous decays of internally hot copper and silver dimer anions, ${\mathrm{Cu}}_{2}^{\ensuremath{-}}$ ${\mathrm{Ag}}_{2}^{\ensuremath{-}}$, stored in one two ion-beam storage rings Double Electrostatic Ion Ring Experiment (DESIREE) at Stockholm University. A coincidence detection technique was utilized enabling essentially background-free measurements ${\mathrm{Cu}}_{2}^{\ensuremath{-}}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}$ Cu $+ {\mathrm{Cu}}^{\ensuremath{-}}$ ${\mathrm{Ag}}_{2}^{\ensuremath{-}}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}$ Ag {\mathrm{Ag}}^{\ensuremath{-}}$ fragmentation rates. Furthermore, total rates neutral decay products (monomers dimers) were relative contributions electron emission (${\mathrm{Cu}}_{2}^{\ensuremath{-}}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}{\mathrm{Cu}}_{2} + {e}^{\ensuremath{-}}$ ${\mathrm{Ag}}_{2}^{\ensuremath{-}}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}{\mathrm{Ag}}_{2} {e}^{\ensuremath{-}}$) deduced as functions time. Fragmentation is completely dominant early times. However, after about 20 ms storage, observed becomes leading path 100 for both anions. The branching ratios between (vibrationally assisted autodetachment processes) are very nearly same ${\mathrm{Ag}}_{2}^{\ensuremath{-}}$ throughout present cycle 10 seconds. This surprising considering difference affinities dimers, ${\mathrm{Cu}}_{2}$ ${\mathrm{Ag}}_{2}$, dissociation energies.