Krypton energy level diagram

Energy levels and transitions of neutral krypton (Kr I): the 84 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 79 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 krypton

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).

⁸³Kr hyperfine structure (I = 9/2)

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

Isotope shifts

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

Closed and nearly closed transitions of krypton

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 Kr 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, this site's own Cowan-code calculation with the parameters fitted to the NIST energies (HFR fit; inputs and fit report in the repository folder cowan/; used only where nothing else gives a rate; strong lines typically within a factor 2, weak lines worse), or a model calculation.

Kr energy levels

Kr⁺ ionisation limit 112914.43 cm⁻¹ = 13.99961 eV (88.563 nm)

Sources

• Cannon & Janik, Phys. Rev. A 42, 397 (1990) [as quoted in Brandi, Hogervorst, Ubachs, J. …
• Cannon, Phys. Rev. A 47, 1148 (1993) [as quoted in Zhang, Ritterbusch, Hu, Dong, Gao, Jia…
• Dzierzega, Volz, Nave, Griesmann, Phys. Rev. A 62, 022505 (2000) [arXiv:physics/0005057],…
• Dzierzega, Volz, Nave, Griesmann, Phys. Rev. A 62, 022505 (2000) [arXiv:physics/0005057],…
• Gazeli, Aubert, Prasanna, Duluard, Lombardi, Hassouni, arXiv:2012.14685 (2020)
• Husson et al., 'Mesure de constantes de structure hyperfine de niveaux 6p du xenon et 5p …
• Jackson, J. Opt. Soc. Am. 67, 1638 (1977) [as quoted in Zhang, Ritterbusch, Hu, Dong, Gao…
• Lefers et al., Phys. Rev. A 66, 012507 (2002) (abstract)
• NIST ASD
• NIST ASD level energies
• Schmitt, Pisella, Volz, Schmoranzer, ASOS6 abstracts p. 143 (1998), beam-gas-laser spectr…
• Small-Warren & Chiu, Phys. Rev. A 11, 1777 (1975) (abstract)
• Williams, Lu, Rudinger, Xu, Yokochi, Mueller, Phys. Rev. A 83, 012512 (2011) [arXiv:1012.…
• best estimate of the non-beam-gas-laser experimental lifetimes (pulsed-laser and arc data…

Isotope-shift keys 'A-B' mean nu(A) - nu(B). 83Kr values are hyperfine centre of gravity. 81Kr and 85Kr are radioactive ATTA tracers; their nuclear spins were not confirmed in an opened source and are therefore omitted. Level energies are NIST ASD values from data/kr/levels.csv; Paschen names in the labels. Entries marked '(abstract)' were read on the publisher's abstract page only. Added 2026-10-01 (second pass): nuclear spins of 81Kr (7/2) and 85Kr (9/2, derived from listed F values) now given. All 30 5s-5p transition rates and branching fractions are from Dzierzega et al. 2000 (the source NIST uses); A values for lines from 2p1, 2p2, 2p5, 2p10 rest on semi-empirical lifetimes. Ground-state isotope shifts of Brandi et al. are printed as nu(84) - nu(A). The 86Kr level energies of Brandi et al. are from 2002 (older than 20 years). 819 nm shifts for 81, 83, 85 are calculated, not measured.

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