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January 1995

Atomic and Molecular Notation

Please note the style followed in Physical Review A and Physical Review E for atomic and molecular notation.

Elements are roman:
           H, Na, Cl, P, etc.

Superscripts to elements indicate charge states:
           Ca²⁺ (not Ca⁺⁺)
           Ca²⁺* for an excited ion

Presuperscripts and presubscripts to elements indicate atomic mass and atomic number:
           $_{53}^{125}\textrm{I}$

For molecular ions, superscripts and subscripts are staggered:
           H₃⁺, He₂*, (D₂O)_n⁺

Roman numerals following elements are set in small caps with a thin space separating the element and the roman numerals:
           Na I

but with a full space in a series:
           Na I, II, III

Letters denoting atomic configurations are set italic, with a full space between the element and the state:
           Na 3p

(but for a transition there is a thin space between the element and the configuration):
           Na 3p – Na 3d

Superscripts to levels indicating odd and even parity are lowercase italic “oh” and “ee”:
           $^{1}P_{3/2}^{o},^{1}S _{3/2}^{e}$

Thin spaces are inserted for clarity in the following notation for atomic and molecular levels:
           3p³P_1/2, 3 ²P_3/2, A ³Π$_{μ}^{+}$, CO X ¹Σ⁺, He II α

For x rays, the Greek letter is on line:
           Kα, Kβ, Lα, Lβ, Cu Kα, Kα₁

For spectral lines of hydrogen, the Greek letter is a subscript and roman letters indicate the series:
           Balmer series: Hα, Hβ
           Lyman series: Ly-α, Ly-β or
           Lyman series: Lα, Lβ (Ly-α, Ly-β, Lyman-α, Lyman-β are also acceptable)

Note that italic is printed for shells, edges:
           K shell, L shell, K-Auger-electron emission, K edge

The author’s use of parentheses allows notation to be closed up:
           ²S_1/2(F = 1), Br⁺(³P ₂), Ar²⁺(3s²3p⁴), (3p^{5 2}P )Ar⁺

Indicate bonds with a “bond” dash:
           C — N bond
           ${∠}$ (H — O — H) = 70◦

Protons, electrons, and neutrons are indicated with lowercase italics:
           p, e, and n

Nucleon is spelled out.