-
Effective proton-neutron interaction in mirror nuclei
Authors:
Y. M. Xing,
Y. F. Luo,
K. H. Li,
Y. H. Zhang,
J. G. Li,
M. Wang,
Yu. A. Litvinov,
K. Blaum,
X. L. Yan,
T. Liao,
M. Zhang,
X. Zhou
Abstract:
Effective proton-neutron interactions, $V_{pn}$, in mirror nuclei are systematically analyzed using the ground-state atomic masses. A mirror symmetry of $V_{pn}$ is found for bound nuclei with a standard deviation of $σ=32$ keV. However, this mirror symmetry is apparently broken for some mirror-nuclei pairs when a proton-unbound nucleus is involved in extracting the $V_{pn}$ values. Such a mirror-…
▽ More
Effective proton-neutron interactions, $V_{pn}$, in mirror nuclei are systematically analyzed using the ground-state atomic masses. A mirror symmetry of $V_{pn}$ is found for bound nuclei with a standard deviation of $σ=32$ keV. However, this mirror symmetry is apparently broken for some mirror-nuclei pairs when a proton-unbound nucleus is involved in extracting the $V_{pn}$ values. Such a mirror-symmetry breaking is attributed to the Thomas-Ehrman shift of the proton-unbound nucleus and investigated by using the Gamow shell model. It is concluded that the Thomas-Ehrman shift originates mainly from reduced Coulomb energies in the proton-unbound nuclei due to the extended radial density distribution of valence protons.
△ Less
Submitted 3 March, 2025;
originally announced March 2025.
-
$Z=14$ Magicity Revealed by the Mass of the Proton Dripline Nucleus $^{22}$Si
Authors:
Y. M. Xing,
Y. F. Luo,
Y. H. Zhang,
M. Wang,
X. H. Zhou,
J. G. Li,
K. H. Li,
Q. Yuan,
Y. F. Niu,
J. Y. Guo,
J. C. Pei,
F. R. Xu,
G. de Angelis,
Yu. A. Litvinov,
K. Blaum,
I. Tanihata,
T. Yamaguchi,
Y. Yu,
X. Zhou,
H. S. Xu,
Z. Y. Chen,
R. J. Chen,
H. Y. Deng,
C. Y. Fu,
W. W. Ge
, et al. (14 additional authors not shown)
Abstract:
Using the $Bρ$-defined isochronous mass spectrometry technique, we conducted the first mass measurement of the proton dripline nucleus $^{22}$Si. We confirm that $^{22}$Si is bound against particle emission with $S_p/S_{2p}=+1412(114)/+229(54)$ keV, fixing the proton dripline location for the Si element. By analyzing the mass differences of the neighboring $sd$-shell nuclei, we find that $^{22}$Si…
▽ More
Using the $Bρ$-defined isochronous mass spectrometry technique, we conducted the first mass measurement of the proton dripline nucleus $^{22}$Si. We confirm that $^{22}$Si is bound against particle emission with $S_p/S_{2p}=+1412(114)/+229(54)$ keV, fixing the proton dripline location for the Si element. By analyzing the mass differences of the neighboring $sd$-shell nuclei, we find that $^{22}$Si exhibits a doubly-magic character similar to its mirror partner $^{22}$O, and that the mirror energy difference of $^{22}$Si-$^{22}$O deviates from the predictions assuming mirror symmetry. Gamow shell-model calculations reveal that the average occupations of valence protons in $^{22}$Si are nearly identical to those of valence neutrons in $^{22}$O, supporting the $Z=14$ magicity in $^{22}$Si. The observed mirror-symmetry breaking is attributed to the extended proton distribution in $^{22}$Si arising from a small contribution of the unbound $\pi2s_{1/2}$ orbital.
△ Less
Submitted 3 March, 2025;
originally announced March 2025.
-
Nuclear structure of dripline nuclei elucidated through precision mass measurements of $^{23}$Si, $^{26}$P, $^{27,28}$S, and $^{31}$Ar
Authors:
Y. Yu,
Y. M. Xing,
Y. H. Zhang,
M. Wang,
X. H. Zhou,
J. G. Li,
H. H. Li,
Q. Yuan,
Y. F. Niu,
Y. N. Huang,
J. Geng,
J. Y. Guo,
J. W. Chen,
J. C. Pei,
F. R. Xu,
Yu. A. Litvinov,
K. Blaum,
G. de Angelis,
I. Tanihata,
T. Yamaguchi,
X. Zhou,
H. S. Xu,
Z. Y. Chen,
R. J. Chen,
H. Y. Deng
, et al. (17 additional authors not shown)
Abstract:
Using the B$ρ$-defined isochronous mass spectrometry technique, we report the first determination of the $^{23}$Si, $^{26}$P, $^{27}$S, and $^{31}$Ar masses and improve the precision of the $^{28}$S mass by a factor of 11. Our measurements confirm that these isotopes are bound and fix the location of the proton dripline in P, S, and Ar. We find that the mirror energy differences of the mirror-nucl…
▽ More
Using the B$ρ$-defined isochronous mass spectrometry technique, we report the first determination of the $^{23}$Si, $^{26}$P, $^{27}$S, and $^{31}$Ar masses and improve the precision of the $^{28}$S mass by a factor of 11. Our measurements confirm that these isotopes are bound and fix the location of the proton dripline in P, S, and Ar. We find that the mirror energy differences of the mirror-nuclei pairs $^{26}$P-$^{26}$Na, $^{27}$P-$^{27}$Mg, $^{27}$S-$^{27}$Na, $^{28}$S-$^{28}$Mg, and $^{31}$Ar-$^{31}$Al deviate significantly from the values predicted assuming mirror symmetry. In addition, we observe similar anomalies in the excited states, but not in the ground states, of the mirror-nuclei pairs $^{22}$Al-$^{22}$F and $^{23}$Al-$^{23}$Ne. Using $ab~ initio$ VS-IMSRG and mean field calculations, we show that such a mirror-symmetry breaking phenomeon can be explained by the extended charge distributions of weakly-bound, proton-rich nuclei. When observed, this phenomenon serves as a unique signature that can be valuable for identifying proton-halo candidates.
△ Less
Submitted 23 October, 2024;
originally announced October 2024.
-
Ground-state mass of $^{22}$Al and test of state-of-the-art \textit{ab initio} calculations
Authors:
M. Z. Sun,
Y. Yu,
X. P. Wang,
M. Wang,
J. G. Li,
Y. H. Zhang,
K. Blaum,
Z. Y. Chen,
R. J. Chen,
H. Y. Deng,
C. Y. Fu,
W. W. Ge,
W. J. Huang,
H. Y. Jiao,
H. H. Li,
H. F. Li,
Y. F. Luo,
T. Liao,
Yu. A. Litvinov,
M. Si,
P. Shuai,
J. Y. Shi,
Q. Wang,
Y. M. Xing,
X. Xu
, et al. (11 additional authors not shown)
Abstract:
The ground-state mass excess of the $T_{z}=-2$ drip-line nucleus $^{22}$Al is measured for the first time to be $18103(10)$ keV using the newly-developed B$ρ$-defined isochronous mass spectrometry method at the cooler storage ring in Lanzhou. The new mass excess value allowed us to determine the excitation energies of the two low-lying $1^+$ states in $^{22}$Al with significantly reduced uncertain…
▽ More
The ground-state mass excess of the $T_{z}=-2$ drip-line nucleus $^{22}$Al is measured for the first time to be $18103(10)$ keV using the newly-developed B$ρ$-defined isochronous mass spectrometry method at the cooler storage ring in Lanzhou. The new mass excess value allowed us to determine the excitation energies of the two low-lying $1^+$ states in $^{22}$Al with significantly reduced uncertainties of 51 keV. Comparing to the analogue states in its mirror nucleus $^{22}$F, the mirror energy differences of the two $1^+$ states in the $^{22}$Al-$^{22}$F mirror pair are determined to be $-625(51)$ keV and $-330(51)$ keV, respectively. The excitation energies and the mirror energy differences are used to test the state-of-the-art \textit{ab initio} valence-space in-medium similarity renormalization group calculations with four sets of interactions derived from the chiral effective field theory. The mechanism leading to the large mirror energy differences is investigated and attributed to the occupation of the $πs_{1/2}$ orbital.
△ Less
Submitted 26 January, 2024;
originally announced January 2024.
-
$Bρ$-defined isochronous mass spectrometry: a new approach for high-precision mass measurements of short-lived nuclei
Authors:
M. Wang,
M. Zhang,
X. Zhou,
Y. H. Zhang,
Yu. A. Litvinov,
H. S. Xu,
R. J. Chen,
H. Y. Deng,
C. Y. Fu,
W. W. Ge,
H. F. Li,
T. Liao,
S. A. Litvinov,
P. Shuai,
J. Y. Shi,
M. Si,
R. S. Sidhu,
Y. N. Song,
M. Z. Sun,
S. Suzuki,
Q. Wang,
Y. M. Xing,
X. Xu,
T. Yamaguchi,
X. L. Yan
, et al. (4 additional authors not shown)
Abstract:
A novel technique for broadband high-precision mass measurements of short-lived exotic nuclides is reported. It is based on the isochronous mass spectrometry (IMS) and realizes simultaneous determinations of revolution time and velocity of short-lived stored ions at the cooler storage ring CSRe in Lanzhou. The new technique, named as the $Bρ$-defined IMS or $Bρ$-IMS, boosts the efficiency, sensiti…
▽ More
A novel technique for broadband high-precision mass measurements of short-lived exotic nuclides is reported. It is based on the isochronous mass spectrometry (IMS) and realizes simultaneous determinations of revolution time and velocity of short-lived stored ions at the cooler storage ring CSRe in Lanzhou. The new technique, named as the $Bρ$-defined IMS or $Bρ$-IMS, boosts the efficiency, sensitivity, and accuracy of mass measurements, and is applied here to measure masses of neutron-deficient $fp$-shell nuclides. In a single accelerator setting, masses of $^{46}$Cr, $^{50}$Fe and $^{54}$Ni are determined with relative uncertainties of (5~-~6)$\times10^{-8}$, thereby improving the input data for testing the unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. This is the technique of choice for future high-precision measurements of the most rarely produced shortest-lived nuclides.
△ Less
Submitted 3 November, 2022;
originally announced November 2022.
-
$Bρ$-defined Isochronous Mass Spectrometry and Mass Measurements of $^{58}$Ni Fragments
Authors:
M. Zhang,
X. Zhou,
M. Wang,
Y. H. Zhang,
Yu. A. Litvinov,
H. S. Xu,
R. J. Chen,
H. Y. Deng,
C. Y. Fu,
W. W. Ge,
H. F. Li,
T. Liao,
S. A. Litvinov,
P. Shuai,
J. Y. Shi,
R. S. Sidhu,
Y. N. Song,
M. Z. Sun,
S. Suzuki,
Q. Wang,
Y. M. Xing,
X. Xu,
T. Yamaguchi,
X. L. Yan,
J. C. Yang
, et al. (3 additional authors not shown)
Abstract:
A novel isochronous mass spectrometry, termed as $Bρ$-defined IMS, is established at the experimental cooler-storage ring CSRe in Lanzhou. Its potential has been studied through high precision mass measurements of $^{58}$Ni projectile fragments. Two time-of-flight detectors were installed in one of the straight sections of CSRe, thus enabling simultaneous measurements of the velocity and the revol…
▽ More
A novel isochronous mass spectrometry, termed as $Bρ$-defined IMS, is established at the experimental cooler-storage ring CSRe in Lanzhou. Its potential has been studied through high precision mass measurements of $^{58}$Ni projectile fragments. Two time-of-flight detectors were installed in one of the straight sections of CSRe, thus enabling simultaneous measurements of the velocity and the revolution time of each stored short-lived ion. This allows for calculating the magnetic rigidity $Bρ$ and the orbit length $C$ of each ion. The accurate $Bρ(C)$ function has been constructed, which is a universal calibration curve used to deduce the masses of the stored nuclides. The sensitivity to single stored ions, quickness, and background-free characteristics of the method are ideally suited to address nuclides with very short lifetimes and tiniest production yields. In the limiting case of just a single particle, the attained mass resolving power allows one us to determine its mass-over-charge ratio $m/q$ with a remarkable precision of merely $\sim5$ keV. Masses of $T_z = -3/2$ fp-shell nuclides are re-determined with high accuracy, and the validity of the isospin multiplet mass equation is tested up to the heaviest isospin quartet with $A = 55$. The new masses are also used to investigate the mirror symmetry of empirical residual proton-neutron interactions.
△ Less
Submitted 12 September, 2022;
originally announced September 2022.
-
Particle identification and revolution time corrections for the isochronous mass spectrometry in storage rings
Authors:
Y. M. Xing,
Y. H. Zhang,
M. Wang,
Yu. A. Litvinov,
R. J. Chen,
X. C. Chen,
C. Y. Fu,
H. F. Li,
P. Shuai,
M. Si,
M. Z. Sun,
X. L. Tu,
Q. Wang,
H. S. Xu,
X. Xu,
X. L. Yan,
J. C. Yang,
Y. J. Yuan,
Q. Zeng,
P. Zhang,
M. Zhang,
X. Zhou,
X. H. Zhou
Abstract:
In the isochronous mass spectrometry (IMS) performed at storage rings, masses of short-lived nuclides are determined through precision measurements of their mean revolution times. However, the distribution of revolution times could be seriously deteriorated by instabilities of the ring's magnetic fields. This becomes a significant obstacle for the particle identifications and mass determinations.…
▽ More
In the isochronous mass spectrometry (IMS) performed at storage rings, masses of short-lived nuclides are determined through precision measurements of their mean revolution times. However, the distribution of revolution times could be seriously deteriorated by instabilities of the ring's magnetic fields. This becomes a significant obstacle for the particle identifications and mass determinations. A data analysis method is described in this paper which is able to largely remove the uncertainties caused by the magnetic field instabilities in the particle identifications and the mean revolution times. We show that this method is very effective for the IMS experiments even when the magnetic fields of a storage ring vary slowly up to a level of $ΔB/B\sim 10^{-4}$.
△ Less
Submitted 27 October, 2020;
originally announced October 2020.
-
Measurement of $^{58}$Ni($p$, $p$)$^{58}$Ni elastic scattering at low momentum transfer by using the HIRFL-CSR heavy-ion storage ring
Authors:
K. Yue,
J. T. Zhang,
X. L. Tu,
C. J. Shao,
H. X. Li,
P. Ma,
B. Mei,
X. C. Chen,
Y. Y. Yang,
X. Q. Liu,
Y. M. Xing,
K. H. Fang,
X. H. Li,
Z. Y. Sun,
M. Wang,
P. Egelhof,
Yu. A. Litvinov,
K. Blaum,
Y. H. Zhang,
X. H. Zhou
Abstract:
The very first in-ring reaction experiment at the HIRFL-CSR heavy-ion storage ring, namely proton elastic scattering on stable $^{58}$Ni nuclei, is presented. The circulating $^{58}$Ni$^{19+}$ ions with an energy of 95 MeV/u were interacting repeatedly with an internal hydrogen gas target in the CSRe experimental ring. Low energy proton recoils from the elastic collisions were measured with an ult…
▽ More
The very first in-ring reaction experiment at the HIRFL-CSR heavy-ion storage ring, namely proton elastic scattering on stable $^{58}$Ni nuclei, is presented. The circulating $^{58}$Ni$^{19+}$ ions with an energy of 95 MeV/u were interacting repeatedly with an internal hydrogen gas target in the CSRe experimental ring. Low energy proton recoils from the elastic collisions were measured with an ultra-high vacuum compatible silicon-strip detector. Deduced differential cross sections were normalized by measuring K-shell X-rays from $^{58}$Ni$^{19+}$ projectiles due to the $^{58}$Ni$^{19+}$-H$_2$ ionization collisions. Compared to the experimental cross sections, a good agreement has been achieved with the theoretical predictions in the measured region, which were obtained by using the global phenomenological optical model potentials. Our results enable new research opportunities for optical model potential studies on exotic nuclides by using the in-ring reaction setup at the HIRFL-CSR facility.
△ Less
Submitted 26 October, 2020;
originally announced October 2020.
-
Mass measurements for $T_{z}=-2$ $fp$-shell nuclei $^{40}$Ti, $^{44}$Cr, $^{46}$Mn, $^{48}$Fe, $^{50}$Co and $^{52}$Ni
Authors:
C. Y. Fu,
Y. H. Zhang,
M. Wang,
X. H. Zhou,
Yu. A. Litvinov,
K. Blaum,
H. S. Xu,
X. Xu,
P. Shuai,
Y. H. Lam,
R. J. Chen,
X. L. Yan,
X. C. Chen,
J. J. He,
S. Kubono,
M. Z. Sun,
X. L. Tu,
Y. M. Xing,
Q. Zeng,
X. Zhou,
W. L. Zhan,
S. Litvinov,
G. Audi,
T. Uesaka,
T. Yamaguchi
, et al. (4 additional authors not shown)
Abstract:
By using isochronous mass spectrometry (IMS) at the experimental cooler storage ring CSRe, masses of short-lived $^{44}$Cr, $^{46}$Mn, $^{48}$Fe, $^{50}$Co and $^{52}$Ni were measured for the first time and the precision of the mass of $^{40}$Ti was improved by a factor of about 2. Relative precisions of $δm/m=(1-2)\times$10$^{-6}$ have been achieved. Details of the measurements and data analysis…
▽ More
By using isochronous mass spectrometry (IMS) at the experimental cooler storage ring CSRe, masses of short-lived $^{44}$Cr, $^{46}$Mn, $^{48}$Fe, $^{50}$Co and $^{52}$Ni were measured for the first time and the precision of the mass of $^{40}$Ti was improved by a factor of about 2. Relative precisions of $δm/m=(1-2)\times$10$^{-6}$ have been achieved. Details of the measurements and data analysis are described. The obtained masses are compared with the Atomic-Mass Evaluation 2016 (AME$^{\prime}$16) and with theoretical model predictions. The new mass data enable us to extract the higher order coefficients, $d$ and $e$, of the quartic form of the isobaric multiplet mass equation (IMME) for the $fp$-shell isospin quintets. Unexpectedly large $d$- and $e$-values for $A=44$ quintet are found. By re-visiting the previous experimental data on $β$-delayed protons from $^{44}$Cr decay, it is suggested that the observed anomaly could be due to the misidentification of the $T=2$, $J^π=0^{+}$ isobaric analog state (IAS) in $^{44}$V.
△ Less
Submitted 27 September, 2020;
originally announced September 2020.
-
Determination of luminosity for in-ring reactions: A new approach for the low-energy domain
Authors:
Y. M. Xing,
J. Glorius,
L. Varga,
L. Bott,
C. Brandau B. Bruckner,
R. J. Chen,
X. Chen,
S. Dababneh,
T. Davinson,
P. Erbacher,
S. Fiebiger,
T. Gassner,
K. Gobel,
M. Groothuis,
A. Gumberidze,
G. Gyurky,
M. Heil,
R. Hess,
R. Hensch,
P. Hillmann,
P. -M. Hillenbrand,
O. Hinrichs,
B. Jurado,
T. Kausch,
A. Khodaparast
, et al. (37 additional authors not shown)
Abstract:
Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results ar…
▽ More
Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results are in good agreement with an independent measurement based on the x-ray normalization method. Our new method provides an alternative way to precisely measure the luminosity in low-energy stored-beam configurations. This can be of great value in particular in dedicated low-energy storage rings where established methods are difficult or impossible to apply.
△ Less
Submitted 27 August, 2020;
originally announced August 2020.
-
Masses of ground and isomeric states of $^{101}$In and configuration-dependent shell evolution in odd-$A$ indium isotopes
Authors:
X. Xu,
J. H. Liu,
C. X. Yuan,
Y. M. Xing,
M. Wang,
Y. H. Zhang,
X. H. Zhou,
Yu. A. Litvinov,
K. Blaum,
R. J. Chen,
X. C. Chen,
C. Y. Fu,
B. S. Gao,
J. J. He,
S. Kubono,
Y. H. Lam,
H. F. Li,
M. L. Liu,
X. W. Ma,
P. Shuai,
M. Si,
M. Z. Sun,
X. L. Tu,
Q. Wang,
H. S. Xu
, et al. (18 additional authors not shown)
Abstract:
We report first precision mass measurements of the $1/2^-$ isomeric and $9/2^+$ ground states of $^{101}$In. The determined isomeric excitation energy continues a smooth trend of odd-$A$ indium isotopes up to the immediate vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell model calculations only if the neutron configuration mixing is considered. We find that the singl…
▽ More
We report first precision mass measurements of the $1/2^-$ isomeric and $9/2^+$ ground states of $^{101}$In. The determined isomeric excitation energy continues a smooth trend of odd-$A$ indium isotopes up to the immediate vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell model calculations only if the neutron configuration mixing is considered. We find that the single particle energies are different for different states of the same isotope. The presented configuration-dependent shell evolution, type II shell evolution, in odd-$A$ nuclei is discussed for the first time. Our results will facilitate future studies of single-particle neutron states.
△ Less
Submitted 10 July, 2019;
originally announced July 2019.
-
Improving the resolving power of Isochronous Mass Spectrometry by employing an in-ring mechanical slit
Authors:
J. H. Liu,
X. Xu,
P. Zhang,
P. Shuai,
X. L. Yan,
Y. H. Zhang,
M. Wang,
Yu. A. Litvinov,
H. S. Xu,
K. Blaum,
T. Bao,
H. Chen,
X. C. Chen,
R. J. Chen,
C. Y. Fu,
D. W. Liu,
W. W. Ge,
R. S. Mao,
X. W. Ma,
M. Z. Sun,
X. L. Tu,
Y. M. Xing,
J. C. Yang,
Y. J. Yuan,
Q. Zeng
, et al. (9 additional authors not shown)
Abstract:
Isochronous Mass Spectrometry (IMS) in heavy-ion storage rings is an excellent experimental method for precision mass measurements of exotic nuclei. In the IMS, the storage ring is tuned in a special isochronous ion-optical mode. Thus, the mass-over-charge ratios of the stored ions are directly reflected by their respective revolution times in first order. However, the inevitable momentum spread o…
▽ More
Isochronous Mass Spectrometry (IMS) in heavy-ion storage rings is an excellent experimental method for precision mass measurements of exotic nuclei. In the IMS, the storage ring is tuned in a special isochronous ion-optical mode. Thus, the mass-over-charge ratios of the stored ions are directly reflected by their respective revolution times in first order. However, the inevitable momentum spread of secondary ions increases the peak widths in the measured spectra and consequently limits the achieved mass precision. In order to achieve a higher mass resolving power, the ring aperture was reduced to 60 mm by applying a mechanical slit system at the dispersive straight section. The momentum acceptance was reduced as well as better isochronous conditions were achieved. The results showed a significant improvement of the mass resolving power reaching $5.2 \times 10^{5}$, though at the cost of about 40\% ion loss.
△ Less
Submitted 28 May, 2019;
originally announced May 2019.
-
Masses of neutron-rich $^{\operatorname{52-54}}$Sc and $^{54,56}$Ti nuclides: The $N=32$ subshell closure in scandium
Authors:
X. Xu,
M. Wang,
K. Blaum,
J. D. Holt,
Yu. A. Litvinov,
A. Schwenk,
J. Simonis,
S. R. Stroberg,
Y. H. Zhang,
H. S. Xu,
P. Shuai,
X. L. Tu,
X. H. Zhou,
F. R. Xu,
G. Audi,
R. J. Chen,
X. C. Chen,
C. Y. Fu,
Z. Ge,
W. J. Huang,
S. Litvinov,
D. W. Liu,
Y. H. Lam,
X. W. Ma,
R. S. Mao
, et al. (14 additional authors not shown)
Abstract:
Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the neutron-rich $^{\operatorname{52-54}}$Sc and $^{54,56}$Ti nuclei. The new mass excess values $ME$($^{52}$Sc) $=$ $-40525(65)$ keV, $ME$($^{53}$Sc) $=$ $-38910(80)$ keV, and $ME$($^{54}$Sc) $=$ $-34485(360)$ keV, deviate from the Atomic Mass Evaluation 2012 by 2.3$σ$, 2.8$σ$, and 1.7$σ$, respectivel…
▽ More
Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the neutron-rich $^{\operatorname{52-54}}$Sc and $^{54,56}$Ti nuclei. The new mass excess values $ME$($^{52}$Sc) $=$ $-40525(65)$ keV, $ME$($^{53}$Sc) $=$ $-38910(80)$ keV, and $ME$($^{54}$Sc) $=$ $-34485(360)$ keV, deviate from the Atomic Mass Evaluation 2012 by 2.3$σ$, 2.8$σ$, and 1.7$σ$, respectively. These large deviations significantly change the systematics of the two-neutron separation energies of scandium isotopes. The empirical shell gap extracted from our new experimental results shows a significant subshell closure at $N = 32$ in scandium, with a similar magnitude as in calcium. Moreover, we present $ab$ $initio$ calculations using the valence-space in-medium similarity renormalization group based on two- and three-nucleon interactions from chiral effective field theory. The theoretical results confirm the existence of a substantial $N = 32$ shell gap in Sc and Ca with a decreasing trend towards lighter isotones, thus providing a consistent picture of the evolution of the $N = 32$ magic number from the $pf$ into the $sd$ shell.
△ Less
Submitted 29 May, 2019;
originally announced May 2019.
-
Approaching the Gamow window with stored ions: Direct measurement of $^{124}$Xe(p,$γ$) in the ESR storage ring
Authors:
J. Glorius,
C. Langer,
Z. Slavkovská,
L. Bott,
C. Brandau,
B. Brückner,
K. Blaum,
X. Chen,
S. Dababneh,
T. Davinson,
P. Erbacher,
S. Fiebiger,
T. Gaßner,
K. Göbel,
M. Groothuis,
A. Gumberidze,
G. Gyürky,
M. Heil,
R. Hess,
R. Hensch,
P. Hillmann,
P. -M. Hillenbrand,
O. Hinrichs,
B. Jurado,
T. Kausch
, et al. (41 additional authors not shown)
Abstract:
We report the first measurement of low-energy proton-capture cross sections of $^{124}$Xe in a heavy ion storage ring. $^{124}$Xe$^{54+}$ ions of five different beam energies between 5.5 AMeV and 8 AMeV were stored to collide with a windowless hydrogen target. The $^{125}$Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window f…
▽ More
We report the first measurement of low-energy proton-capture cross sections of $^{124}$Xe in a heavy ion storage ring. $^{124}$Xe$^{54+}$ ions of five different beam energies between 5.5 AMeV and 8 AMeV were stored to collide with a windowless hydrogen target. The $^{125}$Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and X-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron- and $γ$-widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.
△ Less
Submitted 6 February, 2019;
originally announced February 2019.
-
Application of isochronous mass spectrometry for the study of angular momentum population in projectile fragmentation reactions
Authors:
X. L. Tu,
A. Kelic-Heil,
Yu. A. Litvinov,
Zs. Podolyak,
Y. H. Zhang,
W. J. Huang,
H. S. Xu,
K. Blaum,
F. Bosch,
R. J. Chen,
X. C. Chen,
C. Y. Fu,
B. S. Gao,
Z. Ge,
Z. G. Hu,
D. W. Liu,
S. A. Litvinov,
X. W. Ma,
R. S. Mao,
B. Mei,
P. Shuai,
B. H. Sun,
Y. Sun,
Z. Y. Sun,
P. M. Walker
, et al. (15 additional authors not shown)
Abstract:
Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional gamma-ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I = 19/2 states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population follo…
▽ More
Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional gamma-ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I = 19/2 states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population following the projectile fragmentation of 78Kr at energies of 480A MeV on a beryllium target. The 19/2 state isomeric ratios of 53Fe produced from different projectiles in the literature have also been extracted as a function of mass number difference between projectile and fragment (mass loss). The results are compared to ABRABLA07 model calculations. The isomeric ratios of 53Fe produced using different projectiles suggest that the theory underestimates not only the previously reported dependence on the spin but also the dependence on the mass loss.
△ Less
Submitted 22 November, 2018;
originally announced November 2018.
-
Isochronous mass measurements of $T_z=-1$ $fp$-shell nuclei from projectile fragmentation of $^{58}$Ni
Authors:
Y. H. Zhang,
P. Zhang,
X. H. Zhou,
M. Wang,
Yu. A. Litvinov,
H. S. Xu,
X. Xu,
P. Shuai,
Y. H. Lam,
R. J. Chen,
X. L. Yan,
T. Bao,
X. C. Chen,
H. Chen,
C. Y. Fu,
J. J. He,
S. Kubono,
D. W. Liu,
R. S. Mao,
X. W. Ma,
M. Z. Sun,
X. L. Tu,
Y. M. Xing,
Q. Zeng,
X. Zhou
, et al. (11 additional authors not shown)
Abstract:
Atomic masses of seven $T_z=-1$, $fp$-shell nuclei from $^{44}$V to $^{56}$Cu and two low-lying isomers, $^{44m}$V ($J^π=6^+$) and $^{52m}$Co ($J^π=2^+$), have been measured with relative precisions of $1-4\times 10^{-7}$ with Isochronous Mass Spectrometry (IMS) at CSRe. The masses of $^{56}$Cu, $^{52g,52m}$Co, and $^{44m}$V were measured for the first time in this experiment. The Mass Excesses (…
▽ More
Atomic masses of seven $T_z=-1$, $fp$-shell nuclei from $^{44}$V to $^{56}$Cu and two low-lying isomers, $^{44m}$V ($J^π=6^+$) and $^{52m}$Co ($J^π=2^+$), have been measured with relative precisions of $1-4\times 10^{-7}$ with Isochronous Mass Spectrometry (IMS) at CSRe. The masses of $^{56}$Cu, $^{52g,52m}$Co, and $^{44m}$V were measured for the first time in this experiment. The Mass Excesses ($ME^{\prime}$s) of $^{44}$V, $^{48}$Mn, $^{50}$Fe, and $^{54}$Ni are determined with an order of magnitude improved precision compared to the literature values. $^{52g,52m}$Co and $^{56}$Cu are found to be $370$~keV and $400$~keV more bound, respectively, while $^{44g,44m}$V are $\sim 300$~keV less bound than the extrapolations in the Atomic-Mass Evaluation 2012 (AME$^{\prime}$12). The masses of the four $T_z=-1/2$ nuclei $^{45}$V, $^{47}$Cr, $^{49}$Mn, and $^{51}$Fe are re-determined to be in agreement, within the experimental errors, with the recent JYFLTRAP measurements or with the previous IMS measurements in CSRe. Details of the measurements and data analysis are described, and the impact of the new $ME$ values on different aspects in nuclear structure are investigated and discussed.
△ Less
Submitted 22 November, 2018;
originally announced November 2018.
-
A method to measure the transition energy $γ_{t}$ of the isochronously tuned storage ring
Authors:
R. J. Chen,
X. L. Yan,
W. W. Ge,
Y. J. Yuan,
M. Wang,
M. Z. Sun,
Y. M. Xing,
P. Zhang,
C. Y. Fu,
P. Shuai,
X. Xu,
Y. H. Zhang,
T. Bao,
X. C. Chen,
X. J. Hu,
W. J. Huang,
H. F. Li,
J. H. Liu,
Yu. A. Litvinov,
S. A. Litvinov,
L. J. Mao,
B. Wu,
H. S. Xu,
J. C. Yang,
D. Y. Yin
, et al. (5 additional authors not shown)
Abstract:
The Isochronous Mass Spectrometry (IMS) is a powerful technique developed in heavy-ion storage rings for measuring masses of very short-lived exotic nuclei. The IMS is based on the isochronous setting of the ring. One of the main parameters of this setting is the transition energy $γ_{t}$. %The transition energy $γ_{t}$ plays an important role in the isochronous mass spectrometry (IMS). It has bee…
▽ More
The Isochronous Mass Spectrometry (IMS) is a powerful technique developed in heavy-ion storage rings for measuring masses of very short-lived exotic nuclei. The IMS is based on the isochronous setting of the ring. One of the main parameters of this setting is the transition energy $γ_{t}$. %The transition energy $γ_{t}$ plays an important role in the isochronous mass spectrometry (IMS). It has been a challenge to determine the $γ_{t}$ and especially to monitor the variation of $γ_{t}$ during experiments. In this paper we introduce a method to measure the $γ_{t}$ online during IMS experiments by using the acquired experimental data. Furthermore, since the storage ring has (in our context) a relatively large momentum acceptance, the variation of the $γ_{t}$ across the ring acceptance is a source of systematic uncertainty of measured masses. With the installation of two time-of-flight (TOF) detectors, the velocity of each stored ion and its revolution time are simultaneously available for the analysis. These quantities enabled us to determine the $γ_{t}$ as a function of orbital length in the ring. The presented method is especially important for future IMS experiments planned at the new-generation storage ring facilities FAIR in Germany and HIAF in China.
△ Less
Submitted 22 November, 2018;
originally announced November 2018.
-
The Masses of the $T_z=-3/2$ Nuclei $^{27}$P and $^{29}$S
Authors:
C. Y. Fu,
Y. H. Zhang,
X. H. Zhou,
M. Wang,
Yu. A. Litvinov,
K. Blaum,
H. S. Xu,
X. Xu,
P. Shuai,
Y. H. Lam,
R. J. Chen,
X. L. Yan,
T. Bao,
X. C. Chen,
H. Chen,
J. J. He,
S. Kubono,
D. W. Liu,
R. S. Mao,
X. W. Ma,
M. Z. Sun,
X. L. Tu,
Y. M. Xing,
P. Zhang,
Q. Zeng
, et al. (11 additional authors not shown)
Abstract:
Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the $T_z=-3/2$ nuclei $^{27}$P and $^{29}$S. The new mass excess value $ME$($^{29}$S) $=-3094(13)$~keV is 66(52)~keV larger than the result of the previous $^{32}$S($^3$He,$^{6}$He)$^{29}$S reaction measurement in 1973 and a factor of 3.8 more precise. The new result for $^{29}$S, together with those o…
▽ More
Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the $T_z=-3/2$ nuclei $^{27}$P and $^{29}$S. The new mass excess value $ME$($^{29}$S) $=-3094(13)$~keV is 66(52)~keV larger than the result of the previous $^{32}$S($^3$He,$^{6}$He)$^{29}$S reaction measurement in 1973 and a factor of 3.8 more precise. The new result for $^{29}$S, together with those of the $T=3/2$ isobaric analog states (IAS) in $^{29}$P, $^{29}$Si, and $^{29}$Al, fit well into the quadratic form of the Isobaric Multiplet Mass Equation IMME. The mass excess of $^{27}$P has been remeasured to be $ME(^{27}$P$)=-685(42)$ keV. By analyzing the linear and quadratic coefficients of the IMME in the $T_z=-3/2$ $sd$-shell nuclei, it was found that the ratio of the Coulomb radius parameters is $R\approx0.96$ and is nearly the same for all $T=3/2$ isospin multiplets. Such a nearly constant $R$-value, apparently valid for the entire light mass region with $A>9$, can be used to set stringent constraints on the isovector and isotensor components of the isospin non-conserving forces in theoretical calculations.
△ Less
Submitted 29 June, 2018;
originally announced June 2018.
-
First application of combined isochronous and Schottky mass spectrometry: Half-lives of fully ionized 49Cr24+ and 53Fe26+ atoms
Authors:
X. L. Tu,
X. C. Chen,
J. T. Zhang,
P. Shuai,
K. Yue,
X. Xu,
C. Y. Fu,
Q. Zeng,
X. Zhou,
Y. M. Xing,
J. X. Wu,
R. S. Mao,
L. J. Mao,
K. H. Fang,
Z. Y. Sun,
M. Wang,
J. C. Yang,
Yu. A. Litvinov,
K. Blaum,
Y. H. Zhang,
Y. J. Yuan,
X. W. Ma,
X. H. Zhou,
H. S. Xu
Abstract:
Lifetime measurements of b -decaying highly charged ions have been performed in the storage ring CSRe by applying the isochronous Schottky mass spectrometry. The fully ionized 49Cr and 53Fe ions were produced in projectile fragmentation of 58Ni primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensi…
▽ More
Lifetime measurements of b -decaying highly charged ions have been performed in the storage ring CSRe by applying the isochronous Schottky mass spectrometry. The fully ionized 49Cr and 53Fe ions were produced in projectile fragmentation of 58Ni primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensities of stored uncooled 49Cr24+ and 53Fe26+ ions. The extracted half-lives T1/2(49Cr24+) = 44.0(27) min and T1/2(53Fe26+) = 8.47(19) min are in excellent agreement with the literature half-life values corrected for the disabled electron capture branchings. This is an important proof-of-principle step towards realizing the simultaneous mass and lifetime measurements on exotic nuclei at the future storage ring facilities.
△ Less
Submitted 8 April, 2018;
originally announced April 2018.
-
Mass Measurements of Neutron-Deficient Y, Zr, and Nb Isotopes and Their Impact on $rp$ and $νp$ Nucleosynthesis Processes
Authors:
Y. M. Xing,
K. A. Li,
Y. H. Zhang,
X. H. Zhou,
M. Wang,
Yu. A. Litvinov,
K. Blaum,
S. Wanajo,
S. Kubono,
G. Martínez-Pinedo,
A. Sieverding,
R. J. Chen,
P. Shuai,
C. Y. Fu,
X. L. Yan,
W. J. Huang,
X. Xu,
X. D. Tang,
H. S. Xu,
T. Bao,
X. C. Chen,
B. S. Gao,
J. J. He,
Y. H. Lam,
H. F. Li
, et al. (26 additional authors not shown)
Abstract:
Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of $^{82}$Zr and $^{84}$Nb were measured for the first time with an uncertainty of $\sim 10$ keV, and the masses of $^{79}$Y, $^{81}$Zr, and $^{83}$Nb were re-determined with a higher precision. %The latter differ significantly from their literature values. The latter are significantly less bound than…
▽ More
Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of $^{82}$Zr and $^{84}$Nb were measured for the first time with an uncertainty of $\sim 10$ keV, and the masses of $^{79}$Y, $^{81}$Zr, and $^{83}$Nb were re-determined with a higher precision. %The latter differ significantly from their literature values. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low $α$ separation energies for neutron-deficient Mo and Tc isotopes, making the formation of Zr-Nb cycle in the $rp$-process unlikely. The new proton separation energy of $^{83}$Nb was determined to be 490(400)~keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the $p$-nucleus $^{84}$Sr relative to the neutron-deficient molybdenum isotopes in the previous $νp$-process simulations.
△ Less
Submitted 6 April, 2018;
originally announced April 2018.
-
Identification of the Lowest $T=2$, $J^{π=}0^+$ Isobaric Analog State in $^{52}$Co and Its Impact on the Understanding of $β$-Decay Properties of $^{52}$Ni
Authors:
X. Xu,
P. Zhang,
P. Shuai,
R. J. Chen,
X. L. Yan,
Y. H. Zhang,
M. Wang,
Yu. A. Litvinov,
H. S. Xu,
T. Bao,
X. C. Chen,
H. Chen,
C. Y. Fu,
S. Kubono,
Y. H. Lam,
D. W. Liu,
R. S. Mao,
X. W. Ma,
M. Z. Sun,
X. L. Tu,
Y. M. Xing,
J. C. Yang,
Y. J. Yuan,
Q. Zeng,
X. Zhou
, et al. (13 additional authors not shown)
Abstract:
Masses of $^{52g,52m}$Co were measured for the first time with an accuracy of $\sim 10$ keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous $β$-$γ$ measurements of $^{52}$Ni, the $T=2$, $J^π=0^+$ isobaric analog state (IAS) in $^{52}$Co was newly assigned, questioning the conventional identification of IASs fr…
▽ More
Masses of $^{52g,52m}$Co were measured for the first time with an accuracy of $\sim 10$ keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous $β$-$γ$ measurements of $^{52}$Ni, the $T=2$, $J^π=0^+$ isobaric analog state (IAS) in $^{52}$Co was newly assigned, questioning the conventional identification of IASs from the $β$-delayed proton emissions. Using our energy of the IAS in $^{52}$Co, the masses of the $T=2$ multiplet fit well into the Isobaric Multiplet Mass Equation. We find that the IAS in $^{52}$Co decays predominantly via $γ$ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.
△ Less
Submitted 30 October, 2016;
originally announced October 2016.
-
An improvement of isochronous mass spectrometry: Velocity measurements using two time-of-flight detectors
Authors:
P. Shuai,
X. Xu,
Y. H. Zhang,
H. S. Xu,
Yu. A. Litvinov,
M. Wang,
X. L. Tu,
K. Blaum,
X. H. Zhou,
Y. J. Yuan,
X. L. Yan,
X. C. Chen,
R. J. Chen,
C. Y. Fu,
Z. Ge,
W. J. Huang,
Y. M. Xing,
Q. Zeng
Abstract:
Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum mea…
▽ More
Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum measurement in addition to the revolution period of stored ions is crucial to reduce the influence of the momentum spread on the standard deviation of the revolution period, which would lead to a much improved mass resolving power of IMS. One of the proposals to upgrade IMS is that the velocity of secondary ions could be directly measured by using two time-of-flight (double TOF) detectors installed in a straight section of a storage ring. In this paper, we outline the principle of IMS with double TOF detectors and the method to correct the momentum spread of stored ions.
△ Less
Submitted 1 March, 2016; v1 submitted 25 January, 2016;
originally announced January 2016.
-
Accurate correction of magnetic field instabilities for high-resolution isochronous mass measurements in storage rings
Authors:
P. Shuai,
H. S. Xu,
Y. H. Zhang,
Yu. A. Litvinov,
M. Wang,
X. L. Tu,
K. Blaum,
X. H. Zhou,
Y. J. Yuan,
G. Audi,
X. L. Yan,
X. C. Chen,
X. Xu,
W. Zhang,
B. H. Sun,
T. Yamaguchi,
R. J. Chen,
C. Y. Fu,
Z. Ge,
W. J. Huang,
D. W. Liu,
Y. M. Xing,
Q. Zeng
Abstract:
Isochronous mass spectrometry (IMS) in storage rings is a successful technique for accurate mass measurements of short-lived nuclides with relative precision of about $10^{-5}-10^{-7}$. Instabilities of the magnetic fields in storage rings are one of the major contributions limiting the achievable mass resolving power, which is directly related to the precision of the obtained mass values. A new d…
▽ More
Isochronous mass spectrometry (IMS) in storage rings is a successful technique for accurate mass measurements of short-lived nuclides with relative precision of about $10^{-5}-10^{-7}$. Instabilities of the magnetic fields in storage rings are one of the major contributions limiting the achievable mass resolving power, which is directly related to the precision of the obtained mass values. A new data analysis method is proposed allowing one to minimise the effect of such instabilities. The masses of the previously measured at the CSRe $^{41}$Ti, $^{43}$V, $^{47}$Mn, $^{49}$Fe, $^{53}$Ni and $^{55}$Cu nuclides were re-determined with this method. An improvement of the mass precision by a factor of $\sim 1.7$ has been achieved for $^{41}$Ti and $^{43}$V. The method can be applied to any isochronous mass experiment irrespective of the accelerator facility. Furthermore, the method can be used as an on-line tool for checking the isochronous conditions of the storage ring.
△ Less
Submitted 13 July, 2014;
originally announced July 2014.