Actinium energy level diagram

Energy levels and transitions of neutral actinium (Ac I): the 72 strongest classified lines below 2 µm from the NIST Atomic Spectra Database and the 45 levels they connect, each line with its vacuum wavelength, frequency and, for 71 of them, the reduced dipole matrix element derived from the NIST transition rate. Measured lifetimes, transition rates, hyperfine constants and isotope shifts from the literature are included, each with its citation.

Hover a line or a level to isolate it, click to keep it selected. Scroll to zoom, drag to move.

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

Key transitions of actinium

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).

²²⁷Ac hyperfine structure (I = 3/2)

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

Isotope shifts

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

Closed and nearly closed transitions of actinium

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.

Listed Ac 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.

Ac energy levels

Ac⁺ ionisation limit 43394.52 cm⁻¹ = 5.38023 eV (230.444 nm)

Sources

• Ferrer, Barzakh, Bastin, Beerwerth, Block, et al., Nat. Commun. 8, 14520 (2017), Table 2 …
• Ferrer, Barzakh, Bastin, Beerwerth, Block, et al., Nat. Commun. 8, 14520 (2017), Table 2,…
• Kramida, Atoms 10, 42 (2022), Table 1: from the measured lifetime 668(11) ns of Zhang et …
• Kramida, Atoms 10, 42 (2022), Table 2 (column 'TW'), read in the Europe PMC full text. No…
• Kramida, Atoms 10, 42 (2022), Table 2 (column 'TW'), read in the Europe PMC full text. No…
• Kramida, Atoms 10, 42 (2022), Table 2 (column 'TW'), read in the Europe PMC full text. No…
• Kramida, Atoms 10, 42 (2022), Table 2 (column 'TW'), read in the Europe PMC full text. No…
• Kramida, Atoms 10, 42 (2022), Table 2 (column 'TW'), read in the Europe PMC full text. No…
• NIST ASD
• NIST ASD level energies
• Sonnenschein, PhD thesis 'Laser developments and high resolution resonance ionization spe…
• Sonnenschein, PhD thesis 'Laser developments and high resolution resonance ionization spe…
• Sonnenschein, PhD thesis 'Laser developments and high resolution resonance ionization spe…
• Sonnenschein, PhD thesis 'Laser developments and high resolution resonance ionization spe…
• Sonnenschein, PhD thesis 'Laser developments and high resolution resonance ionization spe…
• Zhang, Studer, Weber, Gadelshin, Kneip, Raeder, Budker, Wendt, Kieck, Porsev, Cheung, Saf…
• Zhang, Studer, Weber, Gadelshin, Kneip, Raeder, Budker, Wendt, Kieck, Porsev, Cheung, Saf…
• Zhang, Studer, Weber, Gadelshin, Kneip, Raeder, Budker, Wendt, Kieck, Porsev, Cheung, Saf…

Actinium has no stable isotope; the site isotope is presumably 227Ac (I = 3/2, 21.77 y). Hyperfine constants from Sonnenschein's thesis carry statistical errors only. In Ferrer/Granados the first bracket is a 2-sigma statistical error and the second a systematic one; where one 'unc' is given here the two were combined in quadrature. Isotope shifts are stored as nu(first) - nu(second) following Verstraelen et al.; see the conflict about the sign in Ferrer et al. Second-step lines of the resonance ionization scheme (434.51 nm, 424.69 nm from the 22801 cm^-1 level) end on autoionizing states that are not in the NIST level list and are not entered. Transition probabilities shown on the site come from NIST ASD, whose Ac I data appear to follow Kramida 2022 (mostly scaled Cowan-code calculations, normalised to the three measured lifetimes).

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-17118 levels, 26 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