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We have studied the outcome of collisions between the hydrated nucleotide anion adenosine 5′-monophosphate (AMP) and sodium. Electron capture leads to hydrogen loss as well as water evaporation regardless of the initial number m of water molecules attached to the parent ion (m≤=16). The yield of dianions with microsecond lifetimes increases strongly with m, which is explained from dielectric screening of the two charges by the water nanodroplet. For comparison, collision induced dissociation results in water losses with no or very little damage of the AMP molecule itself [ABSTRACT FROM AUTHOR]

C602- and C702- dianions have been produced by electrospray of the monoanions and subsequent electron pickup in a Na vapor cell. The dianions were stored in an electrostatic ring and their decay by electron emission was measured up to 1 s after injection. While C702- ions are stable on this time scale, except for a small fraction of the ions which have been excited by gas collisions, most of the C602- ions decay on a millisecond time scale, with a lifetime depending strongly on their internal temperature. The results can be modeled as decay by electron tunneling through a Coulomb barrier, mainly from thermally populated triplet states about 120 meV above a singlet ground state. At times longer than about 100 ms, the absorption of blackbody radiation plays an important role for the decay of initially cold ions. The tunneling rates obtained from the modeling, combined with WKB estimates of the barrier penetration, give a ground-state energy 200±30 meV above the energy of the monoanion plus a free electron and a ground-state lifetime of the order of 20 s. [ABSTRACT FROM AUTHOR]

CRYRING was used to study collision processes between an electron and a negative ion cluster C[sub 4][sup -]. The total detachment cross sections for the production of the neutral 4C, 3C, 2C, and C fragments were measured. The cross sections for pure detachment, and for detachment plus dissociation leading to the production of C[sub 3]+C, 2C[sub 2], and C[sub 2]+2C were extracted using a grid. It was found that the pure detachment process overwhelmingly dominates all other fragmentation processes. The threshold location for the detachment channel is found to be around 6.0 eV. Although the doubly charged negative ion C[sub 4][sup 2-] has received little previous attention, a defined near-threshold resonance observed in the detachment cross section curve, has been associated with the short-lived state C[sub 4][sup 2-] (0.7 fs lifetime). © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We use a novel electrostatic ion storage ring to measure the radiative lifetime of the upper level in the 3p5 2P°1/2 → 3p5 2P°3/2 spontaneous radiative decay in 32S- to be 503 ± 54 sec. This is by orders of magnitude the longest lifetime ever measured in a negatively charged ion. Cryogenic cooling of the storage ring gives a residual-gas pressure of a few times 10-14 mbarat 13 Kand storage of 10 keV sulfur anions for more than an hour. Our experimental results differ by 13δ from the only available theoretical prediction [P. Andersson et al., Phys. Rev. A 73, 032705 (2006)]. [ABSTRACT FROM AUTHOR]

We report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag2-Ag2+e- decays on milliseconds and seconds timescales. This observation is very surprising as there is no avoided crossing between adiabatic energy curves to mediate such a process. The process is weak, yet dominates the decay signal after 100 ms when ensembles of internally hot Ag-2 ions are stored in the cryogenic ion-beam storage ring, DESIREE, for 10 s. The electron emission process is associated with an instantaneous, very large reduction of the vibrational energy of the dimer system. This represents a dramatic deviation from a Born-Oppenheimer description of dimer dynamics. [ABSTRACT FROM AUTHOR]