0000000000010670
AUTHOR
I. Bergström
An isomeric 19+ state of the $$\pi h_{{9 \mathord{\left/ {\vphantom {9 2}} \right. \kern-\nulldelimiterspace} 2}}^2 i_{1{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} vg_{{9 \mathord{\left/ {\vphantom {9 2}} \right. \kern-\nulldelimiterspace} 2}} (j^{ - 2} )_{0^ + }$$ configuration in 85 210 At125 and the question of isospin dependence in the two-particle core polarization
Usingα-particles of energies 35–51 MeV and in-beam conversion electron andγ-spectroscopy techniques, a 4.0±1.7 μs core-excited 19+ isomeric state in210At with ag-factor of 0.737±0.025 has been observed at an excitation energy of 4027.7 keV. The 19+ state is suggested to have the $$\pi h_{{9 \mathord{\left/ {\vphantom {9 2}} \right. \kern-\nulldelimiterspace} 2}}^2 i_{1{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} vg_{{9 \mathord{\left/ {\vphantom {9 2}} \right. \kern-\nulldelimiterspace} 2}} (j^{ - 2} )_{0^ + }$$ configuration with maximum alignment of the angular momenta. The total two-particle core polarization due to theh 9/2 andi 13/2 protons and theg 9/2 n…
The SMILETRAP (Stockholm-Mainz-Ion-LEvitation-TRAP) facility
Described in this paper is an experimental facility which measures atomic masses by using multiply charged ions from an electron beam ion source. The ions are injected into a Penning trap and the cyclotron frequencies measured. A precision of 2×10−9 has been reached using highly charged carbon, nitrogen, oxygen and neon.
SMILETRAP — Atomic mass measurements with ppb accuracy by using highly charged ions
In the SMILETRAP facility externally produced highly charged ions are captured in a Penning trap and utilized for high precision measurements of atomic masses. Accuracy tests on a ppb level have been performed, using highly charged carbon, oxygen and neon ions. In all cases hydrogen ions served as a reference for the calibration and monitoring of the magnetic field in the trap. Deviations smaller than 3 ppb from the expected results were found in mass measurements of the16O and20Ne atomic masses. The proton atomic mass, determined from the reference measurements on hydrogen ions, is in good agreement with the accepted value [1]. A direct mass measurement on the86Kr-isotope, using trapped86K…
The Stockholm–Mainz ion trap project
A new ion trap facility is described which is dedicated to studies of highly charged ions in a Penning trap. Such a trap will be connected to sources of highly charged ions, in particular the electron beam ion source CRYSIS, at the Manne Siegbahn Institute for Physics. The use of highly charged ions in a Penning trap increases the cyclotron frequency with a factor proportional to the charge which leads to a higher resolution. Also, the possibility to vary the charge state makes it possible to search for and identify different systematic effects. Thus, a substantial increase in accuracy can be expected. In addition, the combination of high charge state ions and a Penning trap allows new appl…
Highly-charged ions in a penning trap: mass measurements, etc.
The use of a Penning trap will start a new generation of precision experiments on highly charged ions. The long storage time of the ions in combination with a controlled confinement in a very small volume will enable accuracies in mass determination better than δm/m = 10-8.
High-frequency Ramsey excitation in a Penning trap
The Ramsey excitation method for high-precision mass-measurements of highly-charged ions has been investigated and benchmarked using H2+ ions in the Penning-trap mass-spectrometer SMILETRAP. The reason for using H2+ ions are their high cyclotron frequency which is typical for the highly-charged ions usually used at SMILETRAP. Two-, three- and four-pulse Ramsey excitation data are analyzed with the help of recent theoretical work and are compared with the previously used single-pulse excitation data. An improvement factor of 2.9 in the statistical uncertainty is achieved. Furthermore the mass of 76Se, included in the previous Q-value measurement of the 76Ge neutrinoless double beta decay, is…
Direct determination of the mass of28Si as a contribution to a new definition of the kilogram
The mass of 28Si has been determined to be m(28Si) = 27.976 926 57(30) u by comparing the cyclotron frequencies of the singly charged ions 12C+, 12C+3 and 28Si+ in a Penning trap mass spectrometer. The experimental technique and the setup are described. The obtained accuracy as well as possible improvements are discussed. Our measurements are related to current efforts to base the kilogram on atomic properties by using an almost perfect single crystal of silicon.
Accuracy tests of atomic mass measurements in a penning trap using externally produced highly charged ions
The SMILETRAP experimental set-up, a Penning trap mass spectrometer for highly charged ions, is described. Capture and observation of cyclotron frequencies of externally produced highly charged ions is demonstrated. Mass measurements utilizing different charge states and species to verify the consistency of the measurements are presented. A relative uncertainty <3 10−9 is attained in comparisons between highly charged 12C, 14N, 16O, 20Ne and singly charged H, H2 and H3 ions. The current limitations and future developments are discussed.
High-precision mass measurements for fundamental applications using highly-charged ions with SMILETRAP
The Penning trap mass spectrometer SMILETRAP takes advantage of highly-charged ions for high-accuracy mass measurements. In this paper recent mass measurements on Li and Ca ions are presented and their impact on fundamental applications discussed, especially the need for accurate mass values of hydrogen-like and lithium-like ions in the evaluation of the electron g-factor measurements in highly-charged ions is emphasized. Such experiments aim to test bound state quantum electrodynamics. Here the ionic mass is a key ingredient, which can be the limiting factor for the final precision.
New Mass Value forLi7
A high-accuracy mass measurement of $^{7}\mathrm{Li}$ was performed with the SMILETRAP Penning-trap mass spectrometer via a cyclotron frequency comparison of $^{7}\mathrm{Li}^{3+}$ and $\mathrm{H}_{2}{}^{+}$. A new atomic-mass value of $^{7}\mathrm{Li}$ has been determined to be $7.016\text{ }003\text{ }425\text{ }6(45)\text{ }\text{ }\mathrm{u}$ with a relative uncertainty of 0.63 ppb. It has uncovered a discrepancy as large as $14\ensuremath{\sigma}$ ($1.1\text{ }\text{ }\ensuremath{\mu}\mathrm{u}$) deviation relative to the literature value given in the Atomic-Mass Evaluation AME 2003. The importance of the improved and revised $^{7}\mathrm{Li}$ mass value, for calibration purposes in nu…
Precision mass measurements using a penning trap and highly charged ions produced in an electron beam ion source
A method for precision mass measurements in a Penning trap using highly charged ions produced in an electron beam ion source (CRYSIS) has been developed. The cyclotron frequencies for O8+, 7+, 6+, 5+ and Ar18+, 17+, 16+, 15+, 14+, 13+ ions have been determined by the excitation of the sum frequency v+ + v−. In addition to CRYSIS ions, H+, H2+ and He+ ions were produced by electron bombardment of the H2 rest gas or helium gas introduced through an UHV leak valve into an auxiliary ion trap (or a pre-trap). A technique for fast (seconds) interchanging of the ion species in the precision trap has been implemented to reduce the long term magnetic field drift.
The SMILETRAP facility
The SMILETRAP experimental set-up, a Penning trap mass spectrometer for highly charged ions, is described. Capture and observation of cyclotron frequencies of externally produced highly charged ions, rapid interchange of investigated and reference ions and measurements of the rotational kinetic energies are demonstrated. Mass measurements utilizing different charge states and species to verify the consistency of the measurements are presented. A relative uncertainty of about 10−9 is attained in comparisons between highly charged carbon, nitrogen, oxygen, neon and the singly charged hydrogen molecule.
Evidence for Two-Nucleon Polarization in the π(h9/2i13/2)11- ν(j-2)0+ Level in 208Po
From in-beam gamma-ray spectroscopy measurements on the 208Pb(α, 4n)208Po reaction using the Stockholm 225-cm cyclotron, we have concluded that there is an 11-, 8 ns isomeric state in 208Po, which lies 1 175 keV above the π(h 9/2 2)8+ state and that this isomeric state should have the configuration π(h 9/2 i 13/2)11- ν(j -2)0+. Calculations based on the use of empirical two-particle interactions give a position of the 11- level which deviates by about + 100 keV from the experimentally found position. It is suggested that this deviation is mainly due to the difference in the polarization of the 206Pb-and 208Pb-cores by the two aligned h 9/2 and i 13/2 protons.
Precision Measurements of Atomic Masses Using Highly Charged Ions and Atomic Clusters
A high precision Penning trap will be connected to the beam of highly charged ions from the electron beam ion source CRYSIS at the Manne Siegbahn Institute for Physics (MSI) in Stockholm. The first series of experiments aim at accurate mass measurements by exploiting the increase of the cyclotron frequency with the charge state of the trapped ion. Using charged states of about 50 it should be possible to achieve relative mass accuracies for mass doublets better than 10-9. For this high accuracy a Penning trap with low imperfections is needed, as well as a sophisticated beam handling and retardation system for controlled injection of the ions into the trap. In order to minimize the effect of…
On the yrast two proton-two neutron hole states in208Po
High-spin levels in208Po, populated in the208Pb(α,4n)-reaction, were studied usingα-particles in the energy region 41–51 MeV. The energies of levels above the 6+ level have an uncertainty of about 10 keV due to the fact that the 8+→6+ transition has not been observed so far, but this transition has previously been established to be converted neither in theK-shell nor in theL-shells. It was found that the yrast cascade ofγ-rays from a 19+ level at 5896+e keV feeds levels of lower spin which all can be explained as originating from two proton-two neutron hole configurations. In the higher part of the cascade it is mainly the neutron holes which change their configuration, while the lower part…