Chromium-52 energy level diagram

Energy levels and transitions of neutral ⁵²Cr (Cr I, nuclear spin I = 0): the 87 strongest classified lines below 2 µm from the NIST Atomic Spectra Database and the 56 levels they connect, each line with its vacuum wavelength, frequency and, for 87 of them, the reduced dipole matrix element. Level energies come from NIST and refer to the natural isotope mixture; transition rates are 59 measured, 26 NIST, 2 semi-empirical. Hyperfine constants and measured frequencies are those of this isotope.

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

Key transitions of ⁵²Cr

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).

Isotope shifts

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

Closed and nearly closed transitions of ⁵²Cr

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 ⁵²Cr 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, a semi-empirical calculation (Kurucz line list, used only where no measurement or NIST value exists; typically within a factor 2), or a model calculation.

⁵²Cr energy levels

Cr⁺ ionisation limit 54575.60 cm⁻¹ = 6.76651 eV (183.232 nm)

Sources

• Cooper, Gibson, Lawler, J. Quant. Spectrosc. Radiat. Transfer 58, 85 (1997), as tabulated…
• Kurucz, R. L., Can. J. Phys. 89, 417 (2011); semi-empirical line list gf2400.pos of 2016-…
• NIST ASD
• NIST ASD Cr I lines table (local copy data/nist/Cr_I_lines_from1nm.tsv)
• NIST ASD level energies
• Sobeck, Lawler, Sneden, Astrophys. J. 667, 1267 (2007)
• Stuhler, Schmidt, Hensler, Werner, Mlynek, Pfau, Phys. Rev. A 64, 031405(R) (2001)
• Stuhler, Schmidt, Hensler, Werner, Mlynek, Pfau, Phys. Rev. A 64, 031405(R) (2001). Note:…
• Stuhler, Schmidt, Hensler, Werner, Mlynek, Pfau, Phys. Rev. A 64, 031405(R) (2001). Note:…

Lifetimes are the Cooper, Gibson, Lawler (1997) LIF values as reprinted in Table 1 of Sobeck et al. 2007 (arXiv version read; 65 of the 131 levels) - method "compilation" because the original was not opened. Transition probabilities are from the machine-readable Table 3 of Sobeck et al. at CDS, restricted to lines the site draws plus all lines from z7P, y7P and z5P; NIST ASD already contains A values of comparable origin for most of them. rme_J_ea0 is derived from A with the SCHEMA convention. 53Cr has negative A in 7S3, 7P4, 5D4, 5D3 (inverted hyperfine structure; F = 9/2 is the lowest ground-state level). Isotope-shift keys are written 53-52 with the sign as printed in the source; where the source did not state its sign convention this is said in the note. Extra fields beyond SCHEMA.md: top-level ionization_limit, laser_cooling_scheme, conflicts; level fields lifetime_other, decay_to_metastable, magnetic_moment_muB; transition fields wavelength_vac_nm (measured, with isotope), linewidth_MHz, saturation_intensity_mW_cm2, doppler_limit_uK. Lifetime entries whose note says LOWER BOUND are bounds. The a5D4 level (8307.5753 cm-1) is not in data/cr/levels.csv but is the main leak / repump state and is included.

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-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