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AARHUS: Exotic charge states in ASTRID

Abstract

Ions are atoms from which one or more orbital electrons have been detached. This removal can be done, for example, by impact of other electrons. Today beams of bare ions - nuclei without any electrons - are available, for example at the GSI heavy ion Laboratory, Darmstadt, even for the heaviest elements. Molecules too can be ionized by removal of one electron and these molecules can be accelerated to form high energy beams. Molecules are, however, generally not expected to be stable when more than one electron is missing, since there is too little negative charge to bind the positive nuclei. It was therefore a surprise when a stable doubly-charged molecular ion was found at experiments at the ASTRID storage ring, Aarhus, Denmark. The aim of the experiment was to measure lifetimes of expected metastable states of doubly-charged carbon monoxide, CO{sup ++}. The CO{sup ++} ions were produced in an ion source and the accelerated beam injected into the storage ring. The circulating intensity was then monitored by detecting neutral species produced in restgas collisions at the end of a straight section. For CO{sup ++}, a fraction of the beam survived for tens of seconds, with a lifetime around 4  More>>
Publication Date:
Apr 15, 1995
Product Type:
Journal Article
Report Number:
INIS-XC-16A0182
Resource Relation:
Journal Name: CERN Courier; Journal Volume: 35; Journal Issue: 3; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 43 PARTICLE ACCELERATORS; ASTRID STORAGE RING; CARBON 12; CARBON 13; CARBON MONOXIDE; CHARGE STATES; DEUTERIUM; DEUTERIUM IONS; ELECTRON BEAMS; ELECTRONS; EXOTIC RESONANCES; METASTABLE STATES; NITROGEN 14
OSTI ID:
22556034
Country of Origin:
CERN
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 0304-288X; CODEN: CECOA2; TRN: XC16A0182127193
Availability:
Available on-line: http://cds.cern.ch/record/1732396/files/vol35-issue3-p018-e.pdf
Submitting Site:
INIS
Size:
page(s) 18-20
Announcement Date:
Jan 09, 2017

Citation Formats

Moller, Soren Pape. AARHUS: Exotic charge states in ASTRID. CERN: N. p., 1995. Web.
Moller, Soren Pape. AARHUS: Exotic charge states in ASTRID. CERN.
Moller, Soren Pape. 1995. "AARHUS: Exotic charge states in ASTRID." CERN.
@misc{etde_22556034,
title = {AARHUS: Exotic charge states in ASTRID}
author = {Moller, Soren Pape}
abstractNote = {Ions are atoms from which one or more orbital electrons have been detached. This removal can be done, for example, by impact of other electrons. Today beams of bare ions - nuclei without any electrons - are available, for example at the GSI heavy ion Laboratory, Darmstadt, even for the heaviest elements. Molecules too can be ionized by removal of one electron and these molecules can be accelerated to form high energy beams. Molecules are, however, generally not expected to be stable when more than one electron is missing, since there is too little negative charge to bind the positive nuclei. It was therefore a surprise when a stable doubly-charged molecular ion was found at experiments at the ASTRID storage ring, Aarhus, Denmark. The aim of the experiment was to measure lifetimes of expected metastable states of doubly-charged carbon monoxide, CO{sup ++}. The CO{sup ++} ions were produced in an ion source and the accelerated beam injected into the storage ring. The circulating intensity was then monitored by detecting neutral species produced in restgas collisions at the end of a straight section. For CO{sup ++}, a fraction of the beam survived for tens of seconds, with a lifetime around 4 seconds. This lifetime was dominated by restgas collisions. The base pressure was around 2 x 10{sup -11} mbar. In order to avoid contamination from molecules with the same mass/charge ratio, e.g. singly-charged nitrogen-14, the carbon monoxide used was based on the naturally rare isotope carbon-13 rather than the abundant carbon-12. Many atoms can also bind an additional electron and form negative ions. Several negative ions are metastable, and lifetime measurements performed at ASTRID and elsewhere produce accurate results important for comparisons with theory. Double-charged negative ions could in principle exist, and indications of metastable states of H{sup -} and O{sup -} were seen some years ago as resonances in the electron bombardment of negative hydrogen ions. This process was recently studied at ASTRID by storing a beam of negative deuterium ions and measuring the electron impact detachment using electrons from the electron cooler. The heavier isotope deuterium was chosen to facilitate the ring operation, and the D{sup -} beam produced in a duoplasmotron source. The production rate was measured from zero relative energy to 20 electronvolts. It shows a threshold at 0.75 electronvolts, but no indications of resonances elsewhere, indicating the non-existence of D{sup -}.}
journal = []
issue = {3}
volume = {35}
journal type = {AC}
place = {CERN}
year = {1995}
month = {Apr}
}