List of levels for 254RF

Author: Balraj Singh | Citation: Nucl. Data Sheets 156, 1 (2019) | Cutoff date: 31-Jan-2019

α dataset in the XUNDL database, compiled from 2015Da12 by J. Chen (NSCL, MSU) was used in this evaluation.

1997He29: ²⁵⁴Rf produced and identified in ²⁰⁶Pb(⁵⁰Ti,2n) reaction, followed by measurement of T_1/2 from SF decay.

Later measurements of half-lives: 2008Dr05, 2015Da12

2008Dr05: ²⁰⁸Pb(⁴⁸Ti,2n),E=4.6-4.8 MeV/nucleon; the beam provided by 88-Inch cyclotron at LBNL. Detected charged particles using a focal plane detector and a double-sided silicon strip detector. Half-life of ²⁵⁴Rf and production cross section measured based on subsequent α decay of ²⁵⁴Rf.

2015Da12: two experiments were performed using ²⁰⁶Pb(⁵⁰Ti,2n) reaction: 1. E=242.5 MeV ⁵⁰Ti beam produced at ATLAS-ANL facility was incident on a 0.5 mg/cm² 99.948% enriched ²⁰⁶Pb target. Recoiling residues were separated and selected using the Fragment Mass Analyzer (FMA) and implanted into a 100 μm-thick, double-sided silicon strip detector (DSSD) at the focal plane. Spontaneous-fission (SF) events were identified based on spatial and temporal correlations between implanted residues and high-energy (>100 MeV) decay events in DSSD. Measured energies of reaction products, conversion electrons, implant-decay correlations. 2. E=244 MeV ⁵⁰Ti beam produced at the LBNL cyclotron facility was incident on a 0.5 mg/cm² ²⁰⁶Pb target. Recoiling residues were separated and selected by the Berkeley Gas-filled Separator (BGS) and implanted into three 1-mm-thick, double-sided silicon-strip detectors (DSSDs), with emitted γ rays detected with a clover HPGe detector behind each DSSD. Measured energies of reaction products, Eγ, Iγ, conversion electrons, implant-decay correlations. Deduced evidence and T_1/2 for two isomers in ²⁵⁴Rf using a novel approach involving a pulse-shape analysis of data acquired with a digital data acquisition system. Comparison with multi-quasiparticle calculations. α total of 28 and 723 SF events from ²⁵⁴Rf were identified in the two experiments, respectively. The two isomers were identified based on observed electron-SF and/or electron-electron-SF correlations following the decay of the isomers, with 82 electrons associated with the shorter-lived 2-qp isomer and 11 electrons with the longer-lived 4-qp isomer. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state

2020Kh01: E(⁵⁰Ti)=242.5 MeV pulsed beam from the UNILAC-GSI facility. This beam energy corresponds E(²⁵⁶Rf^*)=23.3 MeV excitation energy for the compound nucleus. The evaporation residues passed through the gas-filled recoil separator TASCA at GSI. The focal plane detector of TASCA consisted of a multi-wire proportional counter (MWPC) and double-sided silicon strip detectors (DSSDs), and eight DSSDs (box detectors) to detect the backward escaping α particles and fission fragments. Measured energy spectrum of the fission events of ²⁵⁶Rf compound nucleus, spatially and time correlated events from implanted evaporation residues (ERs), fission fragments, α particles, and conversion electrons from the decay of isomeric activity. α total of 22 (ERs)(fission fragment)-correlated events were detected within a time range of 50 μ to 10 s, out of which 20 events were in the correlated time of much less than 1 ms. Small-energy signals were interpreted as arising from the detection of conversion electrons.

2020Kh01 reported one Er-trace, correlated to the fission of ²⁵⁴Rf, with additional two small signals detected, corresponding to the first and second electrons, registered at 0.65 μs and 13.5 μs after the preceding signals, which might indicate decays of two short-lived isomeric states, but with no definite conclusion for the presence of such isomers.

2020SvZZ: ²⁵⁴Rf produced in ²⁰⁶Pb(⁵⁰Ti,2n) reaction at the U400 cyclotron of FLNR, JINR, and fragments separated using SHELS separator. Investigated characteristics of spontaneous fission with measurement of mean number of neutrons per fission for ²⁵⁴Rf ν=3.87 34.

Theoretical nuclear structure calculations:

2022Ma70: calculated negative-parity energy levels, transition dipole, quadrupole and octupole moments using the cluster model of a dinuclear system.

2021Ya34: calculated energy levels, Jπ, deformation parameters, S(2n), charge and neutron radii, neutron skin using the relativistic Hartree-Bogoliubov (RHB) framework.

2020Ta21: calculated superdeformed minima, β₂, β₃, second fission barrier using covariant density functional theory (CDFT).

2018Re07: calculated energies of 2- phonon levels, B(E3) using QRPA with Gogny D1M parametrization.

2015Ag09: calculated binding energies, proton and neutron quadrupole deformations, charge radius, root-mean square (rms) proton radius, neutron skin thickness, S(2n), S(2p) using relativistic Hartree-Bogoliubov theory with DD-PC1 and α(p)-PK1 interactions, and covariant energy density functionals.

2014Af04: calculated kinematic moments of inertia for g.s. rotational band using covariant density functional theory.

2014Li15: calculated level energies, Q(α) values, β₂, β₄ and β₆ for ground and two- and four-quasiparticle high-K isomers, and configuration-constrained potential energy surfaces (PES).

2014Wa25: calculated single-particle levels, deformation parameters, moment of inertia, band crossing using total Routhian surface method.

2012Jo05: calculated level energies and configurations of 2⁺ γ-vibrational states using quasiparticle-phonon model.

2011Jo09: calculated energies, Jπ for collective states using quasiparticle phonon model.

2006Sh19: calculated levels, Jπ, rotational bands, transition dipole and quadrupole moments using cluster model.

2001Mu06: calculated level energy of 2⁺ state, Q(α), α-decay branching ratios using macroscopic-microscopic approach.

Other theoretical calculations (levels, Jπ, bands, B(E|l), decay characteristics for α and SF: 18 references for structure and 39 for decays retrieved from the NSR database are listed in ’document’ records.

Q-value: Estimated uncertainties (2021Wa16): 500 for S(n), 330 for S(p), 200 for Q(α)

Q-value: Q(ε)=3560 300, S(2p)=4250 280, Q(εp)=1550 280 (syst, 2021Wa16). S(2n)=15890 (theory, 2019Mo01)

S(n)= 8510 keV SY	S(p)= 2610 keV SY	Q(α)= 9210 keV SY
Reference: 2021WA16

E(level) (keV)	XREF	J^π(level)	T_1/2(level)	E(γ) (keV)	Final Levels
0	A	0+	22.8 µs 11 % SF ≈ 100 % α < 1.5
48 Calc.	A	(2+)
158 Calc.	A	(4+)
330	A	(6+)		172	158	(4+)
562	A	(8+)		232	330	(6+)
847	A	(10+)		285	562	(8+)
1186	A	(12+)		339	847	(10+)
1570	A	(14+)		384	1186	(12+)
X		(8-)	4.3 µs 10 % IT ≈ 100 % SF < 10
Y		(16+)	247 µs 73 % IT ≈ 100 % SF < 40

E(level) (keV)	J^π(level)	T_1/2(level)	E(γ)	Final Levels
Band 1 - Kπ=0⁺, g.s. band.
48 Calc.	(2+)
158 Calc.	(4+)
330	(6+)
562	(8+)		232	330	(6+)
847	(10+)		285	562	(8+)
1186	(12+)		339	847	(10+)
1570	(14+)		384	1186	(12+)

E(level)	J^π(level)	T_1/2(level)	Comments
0	0+	22.8 µs 11 % SF ≈ 100 % α < 1.5	Only the SF-decay mode has been detected. An upper limit of 1.5% was given by 1997He29 from non-observation of α particles and the total number of 155 SF events detected. E(level): Only the SF-decay mode has been detected. An upper limit of 1.5% was given by 1997He29 from non-observation of α particles and the total number of 155 SF events detected.
48	(2+)		E(level): Kπ=0⁺, g.s. band. Deduced by 2023Se09 from fit to the 172-, 232-, 285-, 339-, and 384 keV γ-ray energies using the Harris formula. The low-energy transition from the level was not seen in the gamma spectrum as it is expected to be heavily converted.
158	(4+)		E(level): Kπ=0⁺, g.s. band. Deduced by 2023Se09 from fit to the 172-, 232-, 285-, 339-, and 384 keV γ-ray energies using the Harris formula. The low-energy transition from the level was not seen in the gamma spectrum as it is expected to be heavily converted.
330	(6+)		E(level): Kπ=0⁺, g.s. band.
562	(8+)		E(level): Kπ=0⁺, g.s. band.
847	(10+)		E(level): Kπ=0⁺, g.s. band.
1186	(12+)		E(level): Kπ=0⁺, g.s. band.
1570	(14+)		E(level): Kπ=0⁺, g.s. band.
X	(8-)	4.3 µs 10 % IT ≈ 100 % SF < 10	α cluster of three counts at 853 keV and two counts at 829 keV is seen in the spectrum of γ rays coincident with electrons, indicating two other possible transitions associated with the 2-qp isomer (2015Da12). E(level): α cluster of three counts at 853 keV and two counts at 829 keV is seen in the spectrum of γ rays coincident with electrons, indicating two other possible transitions associated with the 2-qp isomer (2015Da12).
Y	(16+)	247 µs 73 % IT ≈ 100 % SF < 40	%SF<40%, deduced by 2015Da12, assuming that all the six fission events in the time interval of the 4-qp isomer decays originated from this isomer, although these six fission events could also be associated with the ground-state fission events following decays of the 4-qp isomer which may have escaped detection. E(level): %SF<40%, deduced by 2015Da12, assuming that all the six fission events in the time interval of the 4-qp isomer decays originated from this isomer, although these six fission events could also be associated with the ground-state fission events following decays of the 4-qp isomer which may have escaped detection.