Figures 1 A diatomic molecule

Vibrational-rotational molecular constants, and structural quantities (harmonic force constant, k, and equilibrium internuclear distance, Re) derived from these constants are listed in Table 1.1 for the electronic ground states of three 

The electronic energy, traditionally denoted by Te or To, is not described by any standard equation, except in the case of Rydberg states, where a modified Rydberg equation 

A rotation-vibration-electronic spectrum is a collection of transitions between an upper state, always denoted by a single prime, with energy 

An electronic band system will consist of (v, v ) vibrational bands, and each vibrational band will contain many rotational lines, which may be organized into rotational branches, one branch for each value of A J — J — J . Whenever a spectroscopist wants to indicate a change in anything (energy, a molecular constant, or a quantum number) using the symbol A, it is always implied that the lower state quantity ( ) is subtracted from the upper state quantity ( ), for example, 

It is conventional, in both spoken and written spectroscopy-ese , always to say or write the quantum numbers of the upper state first (Mulliken, 1930 Jenkins, 1953 Mulliken, 1955 Sheppard, et al, 1987 Schutte, et al, 1997). 

---