Arsenic energy level diagram

Energy levels and transitions of neutral arsenic (As I): the 64 strongest classified lines below 2 µm from the NIST Atomic Spectra Database and the 35 levels they connect, each line with its vacuum wavelength, frequency and, for 29 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 arsenic

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).

⁷⁵As hyperfine structure (I = 3/2)

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

Closed and nearly closed transitions of arsenic

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 As 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.

As energy levels

As⁺ ionisation limit 78950.00 cm⁻¹ = 9.78855 eV (126.662 nm)

Sources

• Andersen, Jorgensen, Sorensen, J. Opt. Soc. Am. 64, 891 (1974) (beam-foil), as quoted in …
• Bengtsson, Berzinsh, Larsson, Svanberg, Astron. Astrophys. 263, 440 (1992), Table 1 (time…
• Bengtsson, Berzinsh, Larsson, Svanberg, Astron. Astrophys. 263, 440 (1992), Table 2
• Berzins, Ubelis, Bziskjans, J. Quant. Spectrosc. Radiat. Transfer 276, 107943 (2021), Tab…
• Bouazza, Guern, Abjean, Bauche, Z. Phys. D 7, 33 (1987), Table 2 'This work' (Fabry-Perot…
• Bouazza, Guern, Abjean, Bauche, Z. Phys. D 7, 33 (1987), as quoted ("Exp. 1987") in Table…
• Holmgren, Phys. Scr. 11, 15 (1975) (relativistic optimised Hartree-Fock-Slater, dipole-le…
• Liu, Yu, Suo, Liu, Sahoo, Phys. Rev. A 108, 032804 (2023), arXiv:2306.15885, Table IX (re…
• NIST ASD
• NIST ASD level energies
• Pendlebury and Smith, Proc. Phys. Soc. 84, 849 (1964) (atomic-beam magnetic resonance; va…
• R. H. Garstang, J. Res. Natl. Bur. Stand. 68A, 61 (1964), Table 20 (intermediate-coupling…
• branching ratio / lifetime

Level energies are the NIST ASD values (data/nist/As_I_levels.tsv). 75As has I = 3/2 and is the only stable isotope. The two resonance-line A values are derived from the absorption oscillator strengths printed by Bengtsson et al. (their laser lifetimes combined with the branching ratios of Lotrian et al. 1980); NIST ASD already lists the same numbers. Hyperfine A constants of the 4p3 2D, 2P levels are second-hand (Bouazza et al. 1987 as quoted by Liu et al. 2023); note the large uncertainty of 2P°3/2. Lifetimes of the 4p3 metastable levels and all forbidden-line rates are THEORY. In the forbidden-line entries A_s is the sum of the calculated M1 and E2 rates and the note gives both parts. Added 2026-10-01 (second pass): magnetic hyperfine constants A of the seven 4p2 5s levels (Bouazza et al. 1987, printed in mK and converted here, 1 mK = 29.979 MHz); 29 measured branching fractions of the 4p2 5s - 4p3 lines (Berzins et al. 2021, open-access copy on the University of Latvia server) and A values for the seven weak branches of the two laser-measured levels; second-hand beam-foil lifetimes for 4P5/2, 2P1/2, 2P3/2, 2D5/2 and a second-hand theory lifetime for 2D3/2. Berzins et al. print A as 'mantissa (power of ten)', e.g. '127 (5)' = 1.27e7 s^-1. Caveat on Bouazza Table 2: the row labels were read from a damaged OCR layer of the scan (rows in printed order: 4P1/2, 2P1/2, 4P3/2, 2P3/2, 2D3/2, 4P5/2, 2D5/2); the 4P3/2 and 2P3/2 labels are the least certain. Transitions between the q

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