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We have measured the spontaneous neutral particle emission from copper-cluster anions (${\mathrm{Cu}}_{n}{}^{\ensuremath{-}}, n=3--6$) stored at cryogenic temperatures in one of the electrostatic ion storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The measured rate of emission from the stored ${\mathrm{Cu}}_{3}{}^{\ensuremath{-}}$ ions follows a single power-law decay for about 1 ms but then decreases much more rapidly with time. The latter behavior may be due to a decrease in the density of available final states in ${\mathrm{Cu}}_{3}$ as the excitation energies of the decaying ions approach the electron detachment threshold. The emissions from ${\mathrm{Cu}}_{4}{}^{\ensuremath{-}}, {\mathrm{Cu}}_{5}{}^{\ensuremath{-}}$, and ${\mathrm{Cu}}_{6}{}^{\ensuremath{-}}$ are well described by sums of two power laws that are quenched by radiative cooling of the stored ions with characteristic times between a few and hundreds of milliseconds. We relate these two-component behaviors to populations of stored ions with higher and lower angular momenta. In a separate experiment, we studied the laser-induced decay of ${\mathrm{Cu}}_{6}{}^{\ensuremath{-}}$ ions that were excited by 1.13- or 1.45-eV photons after 46 ms of storage.

The intrinsic radiative lifetimes of the $5{d}^{10}6{s}^{}^{2}S_{1/2}$ and $5{d}^{9}6{s}^{2} ^{2}D_{3/2}$ bound excited states in the platinum anion ${\text{Pt}}^{\ensuremath{-}}$ have been studied at cryogenic temperatures at the Double ElectroStatic Ion Ring Experiment (DESIREE) facility at Stockholm University. The intrinsic lifetime of the higher-lying $5{d}^{10}6{s}^{} ^{2}S_{1/2}$ state was measured to be $2.54\ifmmode\pm\else\textpm\fi{}0.10\phantom{\rule{0.16em}{0ex}}\mathrm{s}$, while only a lifetime in the range of 50\char21{}200 ms could be estimated for the $5{d}^{9}6{s}^{2} ^{2}D_{3/2}$ fine-structure level. The storage lifetime of the ${\text{Pt}}^{\ensuremath{-}}$ ion beam was measured to be a little over 15 min at a ring temperature of $13\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The present study reports the lifetime of an atomic negative ion in an excited bound state with an electron configuration different from that of the ground state.

The intrinsic lifetime of the upper level in the bound-bound $3{d}^{9}\phantom{\rule{0.16em}{0ex}}4{s}^{2}$ ${}^{2}{D}_{3/2} \ensuremath{\rightarrow} 3{d}^{9}\phantom{\rule{0.16em}{0ex}}4{s}^{2}$ ${}^{2}{D}_{5/2}$ radiative transition in ${\text{Ni}}^{\ensuremath{-}}$ was measured to be $15.1\ifmmode\pm\else\textpm\fi{}0.4\phantom{\rule{0.16em}{0ex}}\mathrm{s}$. The experiment was performed at cryogenic temperatures in one of the ion-beam storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The storage lifetime of the ${\text{Ni}}^{\ensuremath{-}}$ ion beam was measured to be close to 5 min at a ring temperature of 13 K.

We use a novel electrostatic ion storage ring to measure the radiative lifetime of the upper level in the 3p 5 P 2 o 1/2 →3p 5 P 2 o 3/2 spontaneous radiative decay in S − 32 to be 503±54 ...

The electron-detachment cross section was measured for the molecular negative ions ${\mathrm{CN}}^{\ensuremath{-}}$ and ${\mathrm{O}}_{2}^{\ensuremath{-}}$ incident on N${}_{2}$, in the 0.08\char21{}1.2 a.u. velocity region. Our setup uses the gas stripper of a tandem accelerator as a gas chamber. All cross sections present a maximum near 0.4 a.u., a velocity corresponding to the well-known shape-resonance that appears in the electron-N${}_{2}$ collisions. A semiclassical model is employed to analyze the data. The role of this shape resonance is discussed in this article.

We report the direct detection of two metastable H(2^{2}S) atoms coming from the dissociation of a single cold H(2) molecule, in coincidence measurements. The molecular dissociation was induced by electron impact in order to avoid limitations by the selection rules governing radiative transitions. Two detectors, placed close to the collision center, measure the neutral metastable H(2(2)S) through a localized quenching process, which mixes the H(2^{2}S) state with the H(2^{2}P), leading to a Lyman-α detection. Our data show the accomplishment of a coincidence measurement which proves for the first time the existence of the H(2(2)S)-H(2(2)S) dissociation channel.