Appendix A. Notations and conventions used in molecular spectroscopy.

Appendix A. Notations and conventions used in molecular spectroscopy.

This appendix contains some of the notations and conventions used in molecular spectroscopy recommended by various international organizations, including the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP).

Table A.1. Notations and conventions used in molecular spectroscopy [37][36][42][43][44].

Quantum numbers Type of angular momentum Operator Total Z-axis z-axis total orbital angular momentum L ^ = i = 1 N l ^ i L M L Λ = i = 1 N λ i = 0 , 1 , 2 , ( Σ , Π , Δ , ) total electron spin angular momentum S ^ = i = 1 N s ^ i S M S Σ = i = 1 N σ i total electronic angular momentum[a] J ^ a = L ^ + S ^ Ω = i = 1 N ω i =| Λ + Σ | rotational angular momentum R ^ R K R , k R total angular momentum excluding electron and nuclear spins N ^ = J ^ - S ^ = R ^ + L ^ N M N Λ K , k total angular momentum of the molecule excluding nuclear spins J ^ = R ^ + L ^ + S ^ = N ^ + S ^ J M J Ω P nuclear spin angular momentum I ^ I M I total angular momentum F ^ = R ^ + L ^ + S ^ + I ^ F M F total angular momentum excluding nuclear spins and electron orbital angular momentum [b] O ^ = J ^ - L ^ = R ^ + S ^ Single-Particle Angular Momentum Operators single-electron orbital angular momentum l ^ i l i m li λ i = 0 , 1 , 2 , ( σ , π , δ , ) single-electron spin angular momentum s ^ i s i m si σ i single-electron total angular momentum j ^ i j i m ji ω i = λ i + σ i Other Miscellaneous Conventions principle quantum number n , n i Cartesian coordinates in a laboratory-fixed frame of reference X ' , Y ' , Z ' Cartesian coordinates in the center-of-mass frame of reference, parallel to the laboratory-fixed reference frame, X ' , Y ' , Z ' X , Y , Z Cartesian coordinates in the molecule-fixed frame of reference x , y , z

[a] The symbols   J ^ a   [Lefebvre-Brion, p. 72; Brown, p. 229; Atkins, p. 320; Struve, p. 144; Herzberg] and  j ^   [41] are both used for the total electronic angular momentum. Neither are a part of a uniform recommendation [37][36][42][43][44].

[b] The symbol   O ^   [Lefebvre-Brion, p. 72] is not part of a uniform recommendation [37][36][42][43][44]. ______________________________________________________________________________________________________________________