High-precision mass measurement of doubly magic208Pb Kathrin Kromer1Chunhai Lyu1Menno Door1Pavel Filianin1Zolt an Harman1 Jost Herkenho1Wenjia Huang2Christoph H. Keitel1Daniel Lange1 3Yuri

2025-05-06 0 0 1.87MB 8 页 10玖币

侵权投诉

High-precision mass measurement of doubly magic 208Pb

Kathrin Kromer,1, ∗Chunhai Lyu,1Menno Door,1Pavel Filianin,1Zolt´an Harman,1

Jost Herkenhoﬀ,1Wenjia Huang,2Christoph H. Keitel,1Daniel Lange,1, 3 Yuri

N. Novikov,4, 5 Christoph Schweiger,1Sergey Eliseev,1and Klaus Blaum1

1Max-Planck-Institut f¨ur Kernphysik, 69117 Heidelberg, Germany

2Advanced Energy Science and Technology Guangdong Laboratory, Huizhou 516007, China

3Ruprecht-Karls-Universit¨at Heidelberg, 69117 Heidelberg, Germany

4Department of Physics, St Petersburg State University, St Petersburg 198504, Russia

5NRC “Kurchatov Institute”-Petersburg Nuclear Physics Institute, Gatchina 188300, Russia

The absolute atomic mass of 208Pb has been determined with a fractional uncertainty of 7×10−11

by measuring the cyclotron-frequency ratio Rof 208Pb41+ to 132Xe26+ with the high-precision

Penning-trap mass spectrometer Pentatrap and computing the binding energies EPb and EXe

of the missing 41 and 26 atomic electrons, respectively, with the ab initio fully relativistic multi-

conﬁguration Dirac-Hartree-Fock (MCDHF) method. Rhas been measured with a relative precision

of 9 ×10−12.EPb and EXe have been computed with an uncertainty of 9.1 eV and 2.1 eV, respec-

tively, yielding 207.976 650 571(14) u (u = 9.314 941 024 2(28) ×108eV/c2) for the 208Pb neutral

atomic mass. This result agrees within 1.2σwith that from the Atomic-Mass Evaluation (AME)

2020, while improving the precision by almost two orders of magnitude. The new mass value directly

improves the mass precision of 14 nuclides in the region of Z= 81 −84 and is the most precise

mass value with A > 200. Thus, the measurement establishes a new region of reference mass values

which can be used e.g. for precision mass determination of transuranium nuclides, including the

superheavies.

I. INTRODUCTION

Heavy and superheavy nuclides beyond the doubly

magic nucleus of 208Pb can only exist due to nuclear

shell eﬀects holding them together by counteracting the

rapidly increasing Coulomb repulsion with growing pro-

ton number Z[1]. Insight into these quantum-mechanical

nuclear structure eﬀects can be derived from the masses

of such nuclides. In addition to some direct heavy mass

measurements [2–5], a network of nuclear transitions and

relative mass measurements, i.e. the Atomic-Mass Eval-

uation (AME), provides mass values for most heavy and

superheavy nuclides by tracing them back to a few well-

known masses of uranium isotopes [6]. However, no nu-

clide beyond Z= 70 can be found whose mass is known

to a relative precision of better than 2 ×10−9to act as a

precise reference point for these heavy elements. This di-

rectly limits the achievable precision in the heavier mass

regions and can possibly lead to tensions or shifts of the

relative measured masses due to their referencing to only

one reference point. The limitations by mass dependent

shifts can be reduced signiﬁcantly once there is a refer-

ence mass with similar mass known to high precision [7].

The need for new anchor points for the AME arose during

recent mass measurements with TRIGA-TRAP [5, 8] at

the research reactor TRIGA in Mainz, speciﬁcally, an im-

proved absolute mass of 208Pb [9]. Measuring this mass

will also directly improve the masses of several Pb iso-

topes and other nuclides in this mass region [6].

In addition to the impact as a mass reference for other

mass measurements, the mass of 208Pb will soon be

∗kromer@mpi-hd.mpg.de

needed when the magnetic moment, or the g-factor, of

the bound electron of hydrogen-like 208Pb is planned to

be determined by the Penning-trap experiments Alpha-

trap at the MPIK in Heidelberg [10] and Artemis at GSI

Darmstadt [11]. This measurement could be the most

stringent test of bound-state quantum electrodynamics

in strong ﬁelds. The error of the mass of the nucleus,

however, enters the error budget and therefore needs to

be known to high precision [12]. With the results of this

paper, the error of the mass of 208Pb will be negligible in

future g-factor determinations.

Based on the accurate absolute mass of 132Xe [13, 14],

in this paper, we present a determination of the ab-

solute atomic mass of 208Pb with a fractional uncer-

tainty of 7 ×10−11. This is the result of measuring

the cyclotron-frequency ratio of 208Pb41+ and 132Xe26+

with the high-precision Penning-trap mass spectrome-

ter Pentatrap [15, 16] in combination with a com-

putation of the binding energies of the missing 41

and 26 atomic electrons, respectively, using the ab ini-

tio fully relativistic multi-conﬁguration Dirac-Hartree-

Fock (MCDHF) method. The masses of 132Xe26+ and

208Pb41+ can be related to their neutral counterparts via

m132Xe26+=m132Xe−26me+EXe,(1)

m208Pb41+=m208Pb−41me+EPb,(2)

with me= 5.485 799 090 65(16) ×10−4u be-

ing the electron rest mass [17] and m132Xe=

131.904 155 086(10) u being the mass of a neutral 132Xe

atom [13, 14], each has a relative accuracy of 2.9×10−11

and 7.6×10−11, respectively. EXe and EPb are the

binding-energy diﬀerences that represent the energies re-

quired to ionize the outermost 26 and 41 electrons, re-

spectively, from neutral Xe and Pb atoms. With the mass

arXiv:2210.11602v1 [nucl-ex] 20 Oct 2022

ratio

R=m208Pb41+

m132Xe26+(3)

being experimentally measured, one can improve the ac-

curacy of the absolute mass of 208Pb via

m208Pb

=Rm132Xe+ 26me−EXe+ 41me−EPb , (4)

based on the theoretically calculated EXe and EPb. By

improving the mass of 208Pb the masses of other Pb iso-

topes and nearby elements can be improved accordingly

since they are linked via decays of which the energy has

been measured.

II. EXPERIMENTAL AND THEORETICAL

METHODS

If one introduces a charged particle into a magnetic

ﬁeld B, it will describe a free space cyclotron motion with

the frequency ωc=q

mB, with q/m being the charge-to-

mass ratio. The working principle of a Penning trap is

based on a strong homogeneous magnetic ﬁeld in combi-

nation with an electrostatic quadrupole potential. While

the electrostatic potential prevents the ion from escap-

ing in axial direction, forcing it onto an oscillatory axial

motion with frequency ωz, the magnetic ﬁeld forces the

ion in radial direction onto a circular orbit with a mod-

iﬁed cyclotron frequency ω+. The cross product of the

two ﬁelds in the Lorentz equation leads to an additional

slow drift around the trap center called magnetron mo-

tion with frequency ω−. When comparing these three

Penning-trap eigenfrequencies to the movement of a free

charged particle in a purely magnetic ﬁeld, it holds [18]:

ωc=qω2

++ω2

z+ω2

−.(5)

From this equation we can see that the determination

of eigenfrequencies of an ion in a Penning trap can be

used to determine its mass, if the magnetic ﬁeld inside

the trap is known. However, a determination of a mag-

netic ﬁeld of B≈7 T inside a volume of just a few

10 µm3to suﬃcient precision is not possible. Therefore,

a relative measurement is chosen at Pentatrap, using

a reference ion and a sequential measurement scheme to

determine mass ratios [15]. Highly charged ions are used

due to the advantage that with higher q/m the modi-

ﬁed cyclotron frequency increases and can therefore be

measured to a higher relative precision. For each mass

determination a reference nuclide and charge states have

to be chosen that form a q/m doublet with the nuclide of

interest in order to largely suppress systematic eﬀects in

the cyclotron-frequency ratio determination [15, 16]. The

advantage being, that with q/m doublets the same trap-

ping voltage can be used to match the axial frequency to

the detection tank circuit’s resonance frequency. Using

the same trapping voltage reduces systematic shifts due

to trap anharmonicities. In addition, the absolute mass

of the reference nuclide has to be known better than the

aimed uncertainty of the mass of the nuclide of inter-

est. More technical restrictions are posed by the pro-

duction of the reference ion, limited by binding energies

and the availability of probe material. For these reasons,

the near q/m doublet 208Pb41+ (q/m = 0.197 138 e/u)

and 132Xe26+ (q/m = 0.197 113 e/u) [13, 14] was cho-

sen. The 132Xe26+ ion was created from a gaseous natu-

ral source inside a commercial Dresden electron beam ion

trap (DREEBIT) [19, 20]. The DREEBIT is connected

to a beamline with a large bender magnet for q/m se-

lection, see Fig. 1a) upper beamline. The 208Pb41+ ion

was produced in a Heidelberg Compact electron beam

ion trap (compact EBIT) [21] equipped with an in-trap

laser-desorption target of monoisotopic 208Pb [22]. After

ion breeding, the q/m selection was achieved using the

time-of-ﬂight separation technique with fast high-voltage

switches recently developed at the MPIK [23], supplying

the voltages to a Bradbury-Nielson gate [24], see Fig. 1a)

lower beamline. Once the ions were selected and deceler-

ated by two pulsed drift tubes, they were consecutively

trapped in the ﬁrst of Pentatrap’s ﬁve traps and trans-

ported down to their individual traps.

Due to the ﬁve stacked Penning traps available, see

Fig. 1b), a simultaneous measurement in two traps is pos-

sible, increasing the measurement speed by higher statis-

tics and oﬀering up the opportunity for cross checks be-

tween the traps and several analysis methods. Out of the

other three traps, two are needed for ion storage and one

trap is planned for monitoring, however, currently not in

use.

The ion’s frequencies depend on the magnetic ﬁeld and

the electrostatic potential. All environmental inﬂuences

on these quantities need to be stabilized over the duration

of the measurement. For this, the Pentatrap labora-

tory is temperature-stabilized to δT < 50 mK/h and the

height of the liquid helium level zlHe used for cooling the

superconducting magnet, Penning traps, and the detec-

tion system is stabilized to δzlHe <1 mm/h along with

the pressure of helium gas inside the magnet’s bore to

δp < 10 µbar/h [15].

We employ the Fourier-transform ion-cyclotron-

resonance detection technique [25] using cryogenic tank

circuits connected to the Penning traps to pick up the

small image current induced in the trap electrodes by

the ion. The largest frequency ω+, and therefore the

frequency with the highest contribution to the overall

error, is measured using the phase-sensitive pulse and

phase (PnP) method [26, 27]. This method, described in

more detail below, sets an initial phase of the reduced

cyclotron frequency, then the motion is left decoupled

for a variable phase accumulation time tacc during which

the phase can evolve freely, before reading out the ﬁ-

nal phase φmeas. The other two frequencies ωzand ω−

are measured with the Fast-Fourier-Transform (FFT) dip

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

10 玖币 0人已下载

立即下载

摘要：

High-precisionmassmeasurementofdoublymagic208PbKathrinKromer,1,ChunhaiLyu,1MennoDoor,1PavelFilianin,1ZoltanHarman,1JostHerkenho,1WenjiaHuang,2ChristophH.Keitel,1DanielLange,1,3YuriN.Novikov,4,5ChristophSchweiger,1SergeyEliseev,1andKlausBlaum11Max-Planck-InstitutfurKernphysik,69117Heidelberg,Germ...

展开>> 收起<<

High-precision mass measurement of doubly magic208Pb Kathrin Kromer1Chunhai Lyu1Menno Door1Pavel Filianin1Zolt an Harman1 Jost Herkenho1Wenjia Huang2Christoph H. Keitel1Daniel Lange1 3Yuri.pdf

共8页,预览2页

还剩页未读，继续阅读

声明：本站为文档C2C交易模式，即用户上传的文档直接被用户下载，本站只是中间服务平台，本站所有文档下载所得的收益归上传人(含作者)所有。玖贝云文库仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私，请立即通知玖贝云文库，我们立即给予删除！

High-precision mass measurement of doubly magic208Pb Kathrin Kromer1Chunhai Lyu1Menno Door1Pavel Filianin1Zolt an Harman1 Jost Herkenho1Wenjia Huang2Christoph H. Keitel1Daniel Lange1 3Yuri

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

热门标签

举报选择: