Authors: Jun Chen and Balraj Singh |  Citation: Nucl. Data Sheets 177, 1 (2021) |  Cutoff date: 3-Sep-2021 

 Full ENSDF file | Adopted Levels (PDF version) 

Q(β-)=-6441 keV 29S(n)= 8720 keV 30S(p)= -320 keV 28Q(α)= 7454 keV 11
Reference: 2021WA16

  A  198Fr α decay (15 MS)  B  198Fr α decay (1.1 MS):?

General Comments:

1967Tr06: some indication that 194At may have been produced in 185,187Re(20Ne,X),E=100-200 MeV reaction.

1984YaZY: a 0.18 s 8 α activity with Eα=7200 keV 20 was produced in heavy-ion reactions and assigned to 194At by mass separation and αα(t) correlation with daughter nuclei

1995Le15: 194At Activity produced in 141Pr(56Fe,3n),E=256 MeV reaction and separated in a gas-filled recoil mass separator. The measured fine structure of α particles was not definite due to (1995Le15).

2013An03 (also 2009An11): measurement of β-delayed fission in the decay of 194At to 194Po using 259 MeV 56Fe beam with a typical intensity of 400-600 pnA from the UNILAC heavy ion accelerator at GSI. The targets were 141PrF3 with 100% natural abundance. Evaporation residues were separated by the velocity filter SHIP, transported through three time-of-flight detectors and implanted into a position-sensitive silicon detector (PSSD) for detection of subsequent α and fission decays. γ rays were detected with a large-volume four-crystal clover germanium detector. Measured α and fission spectra, time distribution using recoil-fission correlation, reaction yields. Deduced upper limits on TKE, T1/2. Discussed β-delayed fission probability. NβDF/Nα=0.00065 8, where NβDF and Nα are observed counts of β-delayed fissions and α decays of 194Po, respectively. Total beta-delayed fission from both isomers is estimated as ≈1.6%; which is divided here equally amongst the two activities by the evaluators

2013Ny01: 194At produced in 147Sm(51V,4n) E=224 MeV reaction at JYFL, Jyvaskyla accelerator facility followed by separation using RITU separator. Measured Eα, Iα, Eγ, αγ-coin, T1/2 of 194At activities.

2013Uu01: 194At activity from 198Fr α decay, the latter produced 141Pr(60Ni,3n),E=268 MeV reaction at JYFL, Jyvaskyla accelerator facility followed by separation using RITU separator. Measured Eα, Iα, αα-correlations, T1/2 of 194At activity.

2014Gh09: measurement of β-delayed fission in the decay of 194At to 194Po. 194At isotope was produced in spallation reactions with the bombardment of a 50 g/cm2 thick UCx target by 1.4 GeV protons from the CERN On-Line Isotope Mass Separator (ISOLDE) facility. At isotopes were laser ionized and accelerated to 30 keV followed by mass separation. Purified ion beams were transported to the detection station and implanted into 20 μg/cm2 thick carbon foils. Fission fragments and α particles were measured by two silicon detectors of 300 μm thickness and γ rays were detected by a high-purity germanium detectors. Measured Eγ, Iγ, fission fragments. 2014Gh09 measured the counts of b-delayed fissions (NεF) and α decays (Nα), but could not determine the β-delayed fission probability since two states in 194At can decay via ε but their decay branching ratios are unknown. Nα/NεF=2.0 ×103 +17-8 from data with a high-resolution separator (HRS), 1.7 ×103 1 with a general purpose separator (GPS) (2014Gh09)

Theoretical references: consult the NSR database ( for 19 primary references dealing with half-lives in different decay modes and structure calculations.

Levels: %εF: ≈1.6 is estimated by 2013An03 for ε-delayed fission of the two isomers, with ≈0.8 for each if both have similar ε-decay branching ratios (2013An03).

Q-value: S(2n)=19780 40, S(2p)=1760 40, Q(ε)=10288 27, Q(εp)=7879 25 (2021Wa16)

XREFJπ(level) T1/2(level)
  0+XA  (4-,5-) 286 ms 7 
% ε = ?
% α ≈ 100
  0+Y B (9-,10-) 323 ms 7 
% IT = ?
% ε = ?
% α ≈ 100

Jπ(level): Proposed by 2009An11 based on most intense and least hindered α transition, and consideration of possible configurations.

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Additional Level Data and Comments:

  0+X(4-,5-) 286 ms 7 
% ε = ?
% α ≈ 100
Theoretical half-life of 2.09 s for β decay and 0.24 s for α decay (2019Mo01) suggests up to 10% ε+β+ decay, but except for %εF decay of ≈0.8 (2013An03), no other study of 194At β decay is available in literature.

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