Ytterbium-171 energy level diagram

Energy levels and transitions of neutral ¹⁷¹Yb (Yb I, nuclear spin I = 1/2): 18 levels and 26 lines below 2 µm, each with its vacuum wavelength, frequency and, for 18 of them, the reduced dipole matrix element. Level energies come from the NIST Atomic Spectra Database; transition rates are 12 measured, 8 theory. Neutral ytterbium is also the starting point for loading Yb⁺ ion traps by photoionisation.

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Download: diagram (PDF) diagram (SVG) transitions (CSV) levels (CSV) source code

Key transitions of ¹⁷¹Yb

λ, ν from NIST level energies unless a measured frequency for this isotope is available. A: measured value or NIST. Γ/2π: natural linewidth of the upper level, 1/(2πτ).

¹⁷¹Yb hyperfine structure (I = 1/2)

Measured A, B constants; sources in the data file.

Isotope shifts

Shift = ν(first isotope) − ν(second isotope).

Closed and nearly closed transitions of ¹⁷¹Yb

A transition is closed when its upper level can decay only to the level it was excited from, so the atom keeps scattering photons. “closed”: among the levels NIST lists, no other level below the upper level has the opposite parity and |ΔJ| ≤ 1, so no other electric-dipole decay exists. Otherwise the leak is the sum of the branching ratios of the other decay lines of the upper level (or 1 − branching ratio where that of the line itself has been measured), and the number of photons is 1 / leak. “≥” and “≤”: at least one possible decay path has no listed rate, so the leak is a lower limit. These numbers are derived from the branching ratios, lifetimes and rates of this page, not measured as such; the tag names the weakest of the inputs, * marks theory and ≈ a model or semi-empirical calculation. Listed: lines that start on the ground level or on a metastable level and leak at most 10 %, unless more than three possible decay paths have no listed rate. Fine-structure levels only: hyperfine and Zeeman dark states and forbidden decays without a listed rate are not considered. Select a line in the diagram for the full list of its leak channels.

All ¹⁷¹Yb transitions below 2 µm

Reduced dipole matrix elements follow the convention A = ω³|d|²/(3πε₀ħc³(2J′+1)), with J′ the upper level. Tags show where a number comes from: measured, NIST compilation, high-accuracy theory, or a model calculation.

¹⁷¹Yb energy levels

Yb⁺ ionisation limit 50443.20 cm⁻¹ = 6.25416 eV (198.243 nm)

Sources

• 0.352 / 332 ns; as tabulated in Kroeze, Kristensen, Pucher, '171Yb Reference Data', arXiv…
• 0.360 / 13.8 ns; as tabulated in Kroeze, Kristensen, Pucher, '171Yb Reference Data', arXi…
• 1/tau with tau = 21.0(18) s (Siegel 2024; Xu 2014); as tabulated in Kroeze, Kristensen, P…
• 1/tau with tau = 5.464(11) ns (Takasu 2004 et al.), branching to 1S0 = 1 - 6(4)e-8; as ta…
• 1/tau with tau = 872.6(19) ns (weighted mean of 11 measurements); as tabulated in Kroeze,…
• 1/tau with the THEORETICAL tau ~ 8.9 s of Mishra and Balasubramanian (2001); as tabulated…
• A. Yamaguchi, PhD thesis, Kyoto University (2008): 1S0-3P0 frequency (Hoyt 2005) combined…
• Bai and Mossberg, Phys. Rev. A 35, 619 (1987), abstract (read via OpenAlex API record of …
• Bai and Mossberg, Phys. Rev. A 35, 619 (1987), as converted to a reduced matrix element a…
• Baumann, Braun, Gaiser, Liening, J. Phys. B 18, L601 (1985), abstract
• Bowers et al., Phys. Rev. A 53, 3103 (1996), Table I
• Bowers et al., Phys. Rev. A 59, 3513 (1999) and Toepper et al. (unpublished, as quoted by…
• CIPM 2021 recommended value: Margolis et al., Metrologia 61, 035005 (2024); as tabulated …
• Ishiyama, Ono et al., Nature Photonics (2026), arXiv:2505.04154v2, section 'Intrinsic lif…
• Kawasaki et al., Phys. Rev. A 107, L060801 (2023) [arXiv:2303.11665]
• Kawasaki et al., Phys. Rev. A 109, 062806 (2024) [arXiv:2402.13541v2], Table II
• Mishra and Balasubramanian, J. Quant. Spectrosc. Radiat. Transf. 69, 769 (2001); as tabul…
• NIST ASD Yb I lines (local Yb_I_lines.tsv, tp_ref T7227 = D. C. Morton, Astrophys. J. Sup…
• NIST ASD level energies
• Porsev, Rakhlina, Kozlov, Phys. Rev. A 60, 2781 (1999) [arXiv:physics/9903004], Table I
• Porsev, Rakhlina, Kozlov, Phys. Rev. A 60, 2781 (1999) [arXiv:physics/9903004], Table II
• Qiao et al., Results Phys. 48, 106439 (2023); Zhou et al., Phys. Rev. A 101, 062506 (2020…
• Qiao et al., Results Phys. 48, 106439 (2023); as tabulated in Kroeze, Kristensen, Pucher,…
• Zhao et al., Phys. Rev. A 110, 042816 (2024); Ai et al., Phys. Rev. A 107, 063107 (2023) …
• partial decay rate = (theory branching 0.130(13)) / (measured tau = 13.8(17) ns); as tabu…
• partial decay rate = (theory branching 0.508(26)) / (measured tau = 13.8(17) ns); as tabu…
• partial decay rate = (theory branching 0.638(27)) / (measured tau = 332(11) ns); as tabul…
• weighted mean (Birge ratio 1.0) of Zhao 2024, Ai 2023 (+erratum 2024), Beloy 2012, Bowers…
• weighted mean (Birge ratio 1.2) of Beloy 2012; Bowers 1996; Golub 1988; Gustavsson 1979; …
• weighted mean (Birge ratio 1.4) of Baumann et al., J. Phys. B 18, L601 (1985) and Lange, …
• weighted mean (Birge ratio 1.6) of Beloy et al. 2012 and Bowers et al. 1996; as tabulated…
• weighted mean (Birge ratio 2.3) dominated by Takasu et al., Phys. Rev. Lett. 93, 123202 (…
• weighted mean (Birge ratio 2.6) of 11 measurements incl. Jones 2023, Atkinson 2019, McFer…
• weighted mean (Birge ratio 2.9) of Jones et al., Appl. Opt. 62, 3932 (2023); Atkinson 201…
• weighted mean (Birge ratio 3.1) of Qiao 2023 (two papers), Zhou 2020, Wakui 2003, Berends…
• weighted mean (Birge ratio 3.3) of 11 measurements, dominated by Das et al. 2005; excludi…
• weighted mean (Birge ratio 6.3) of Lauprêtre 2020, Tanabe 2018, Kleinert 2016, Nizamani 2…
• weighted mean (Birge ratio 7.3) of Qiao 2023 (Results Phys. 48, 106439), Wakui 2003 (J. P…
• weighted mean of Siegel et al., Phys. Rev. Lett. 132, 133201 (2024) and Xu et al., Phys. …

Primary source: Kroeze, Kristensen, Pucher, '171Yb Reference Data', arXiv:2509.04416v1 (tables parsed from the arXiv HTML; a v2 exists and was not compared). Entries whose source ends with 'as tabulated in Kroeze...' are that paper's weighted means of the original references named (method 'compilation'); its quoted 'Birge ratio' > 1 means the inputs were mutually inconsistent and the uncertainty was inflated. FREQUENCIES: frequency_THz of the main lines refers to the hyperfine CENTRE OF GRAVITY of 171Yb, not to 174Yb and not to a specific F component; NIST level energies used as identifiers are natural-mixture values, so they differ from the 171Yb numbers at the 0.05 cm^-1 level. ISOTOPE SHIFTS are nu(first) - nu(second); values with "derived": true were computed here as differences of tabulated numbers (formula given in the entry's source) and are not printed in any paper. A_s: for 399, 556, 578 nm it equals 1/lifetime of the upper level (branching ~1). For 649, 770, 1389 nm it is the reference paper's 'partial decay rate' = theoretical branching ratio (from Porsev 1999 E1 amplitudes) divided by the measured lifetime, i.e. only semi-experimental. For 680 and 1539 nm the same product was formed here (flagged derived). reduced_matrix_element_au (extra field, units e*a0): convention A_ki = omega^3 |<i||er||k>|^2 / (3 pi eps0 hbar c^3 (2J_k+1)), with k the upper level. Values with method 'theory' are CI+MBPT results of Porsev et al. 1999 (accuracy 3-5% for large amplitudes, 15-2

Atoms with measured data

• Lithium-632 levels, 85 lines
• Lithium-732 levels, 85 lines
• Beryllium-917 levels, 26 lines
• Sodium-2336 levels, 106 lines
• Magnesium-2418 levels, 61 lines
• Magnesium-2518 levels, 61 lines
• Potassium-3934 levels, 84 lines
• Potassium-4034 levels, 84 lines
• Potassium-4134 levels, 84 lines
• Calcium-4035 levels, 61 lines
• Calcium-4335 levels, 61 lines
• Chromium-5256 levels, 87 lines
• Chromium-5356 levels, 87 lines
• Rubidium-8536 levels, 94 lines
• Rubidium-8736 levels, 94 lines
• Strontium-8440 levels, 70 lines
• Strontium-8640 levels, 70 lines
• Strontium-8740 levels, 70 lines
• Strontium-8840 levels, 70 lines
• Cadmium-11115 levels, 21 lines
• Cadmium-11315 levels, 21 lines
• Cadmium-11415 levels, 21 lines
• Caesium-13331 levels, 79 lines
• Barium-13744 levels, 89 lines
• Barium-13844 levels, 89 lines
• Dysprosium-16139 levels, 55 lines
• Dysprosium-16239 levels, 55 lines
• Dysprosium-16339 levels, 55 lines
• Dysprosium-16439 levels, 55 lines
• Erbium-16673 levels, 90 lines
• Erbium-16773 levels, 90 lines
• Erbium-16873 levels, 90 lines
• Thulium-16972 levels, 73 lines
• Ytterbium-17318 levels, 26 lines
• Ytterbium-17418 levels, 26 lines
• Mercury-19927 levels, 47 lines
• Mercury-20127 levels, 47 lines
• Mercury-20227 levels, 47 lines

All elements: periodic table