Isotope shift measurements in the 2s_1/2→ 2p_3/2transition of Be⁺and extraction of the nuclear charge radii for^{7, 10, 11}Be

Abstract

Abstract. We have performed isotope shift measurements in the 2s 1/2 → 2p 3/2 transition of Be + ions using advanced collinear laser spectroscopy with two counterpropagating laser beams. Measurements involving a frequency comb for laser stabilization and absolute frequency determination allowed us to determine the isotope shifts with an accuracy of 2 MHz. From the isotope shifts between 9 Be and 7,10,11 Be, high-accuracy mass shift calculations and the charge radius of the reference isotope 9 Be we determined nuclear charge radii for the isotopes 7,10 Be and the one-neutron halo nucleus 11 Be. The results are compared to nuclear-structure calculations using the Fermionic Molecular Dynamics model which reproduce well the general trend of the radii. Decreasing charge radii from 7 Be to 10 Be are explained by the cluster structure of the nuclei. The increase from 10 Be to 11 Be is mainly caused by the halo neutron by which the 10 Be core moves relative to the center of mass. Polarization of the 10 Be core has only a small influence on the charge radius.

Isotope-shift measurements of stable and short-lived lithium isotopes for nuclear-charge-radii determination

“…The relativistic recoil terms of order α 2 µ/M results from mass scaling, mass polarization, and the Stone terms as expressed by Eqs. (23) and (24). The two sets of results here do not quite agree because the Y&D results include partial contributions from the next-higher-order terms of order α 2 (µ/M) 2 .…”

“…However, the Doppler shift of the transition frequency due to the beam velocity of the accelerated ions, and the limited knowledge of the acceleration voltage with an uncertainty of typically 10 −4 is prohibitive for isotope shift measurements. Recently, such measurements became practicable for Be + ions by using a frequency comb and simultaneous spectroscopy in parallel and antiparallel directions [23,24] in order to eliminate voltage uncertainties. Those studies are still limited by statistical and systematic uncertainties to an accuracy of about 1 MHz, which is not sufficient for lithium isotopes.…”

Collinear laser spectroscopy at ISOLDE: new methods and highlights

“…with ab initio microscopic nuclear structure calculations and conclusions about the shell closure can be found in [40][41][42]. The investigation of both lines of the 2s S 2p P 2 1 2 2 1 2,3 2  fine structure doublet also yielded information on the fine-structure splittings for all isotopes [43].…”

Atomic physics techniques for studying nuclear ground state properties, fundamental interactions and symmetries: status and perspectives

“…Clear evidence was found for intruder states in 31,33 Mg resulting in a disappearance of the shell gap.…”

“…The charge radii of beryllium isotopes including that of the one-neutron halo 11 Be were determined at RIKEN by the group of Wada [30,31] in a Paul trap and at ISOLDE by Nörtershäuser et al [32,33] with higher accuracy using collinear spectroscopy with fluorescence detection. For the first time with laser spectroscopy applied to short-lived nuclei, a frequency comb was used in the ISOLDE experiment in order to measure the resonance frequencies in collinear and anti-collinear geometry, thus eliminating uncertainties in the acceleration voltage of the mass separator.…”