Stuttgart 2012 – wissenschaftliches Programm
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SYIB: Symposium Fast Ion Beams in Nuclear, Atomic and Molecular Physics Research
SYIB 2: Fast Ion Beams in Nuclear, Atomic and Molecular Physics Research II
SYIB 2.4: Hauptvortrag
Dienstag, 13. März 2012, 15:30–16:00, V55.22
Electron Emission from Hot Stored Molecular and Cluster Anions — •Michael Lange1, Klaus Blaum1, Christian Breitenfeldt1,2, Michael Froese1, Sebastian Menk1, Andreas Wolf1, Swarup Das3, and Manas Mukherjee3 — 1Max-Planck-Institut für Kernphysik, Heidelberg — 2Physikalisches Institut, Ernst-Moritz-Arndt-Universität Greifswald — 3Raman Center for Atomic Molecular & Optical Science, Kolkata
Electron emission from excited molecular or cluster anions has been extensively studied in both ion storage rings and traps, which because of the long observation times are ideal tools for such investigations. For a variety of molecular and cluster anions a power law decay was found over a long time interval, followed by a reduction in rate often attributed to radiative quenching. However, evidence for this interpretation has remained circumstantial.
Our cryogenic electrostatic ion beam trap affords a very low residual gas density and, hence, a significant reduction of residual gas-related background in the measured decay rates. This has enabled us to observe the expected deviation from the power law in the decay of SF6− for the first time. Using a statistical rate model we found that this feature can be well reproduced by assuming a sizeable rotational excitation of the anions, which so far has not been fully considered in experiments. Further evidence was found in an experiment on aluminum clusters with 3…7 atoms where after the initial power-law decay and steep decline in rate a second, weaker power-law phase was found that is not readily explained from decay models including radiative relaxation.