Molecular energy levels (Spectroscopy)

 Spectroscopy 

                                                                                   It is the branch of science which deals with the study of interaction of electromagnetic radiation with matter.

Because of such interaction the matter absorbs or emits the energy in discrete amounts called quanta.

The molecule has electronic, vibrational and rotational energy levels. 

ELECTRONIC ENERGY LEVELS:-

The difference between the electronic energy level is very large and hence spacing between them is large. Usually these levels are denoted by  E1, E2, E3.........
The difference between two electronic energy levels goes on decreasing.
i.e (E2-E1) >(E3-E2)
(E3-E2) >(E4-E3)

Electronic energy levels 

VIBRATIONAL ENERGY LEVELS :-

Each electronic energy levels are further sub-divided into group of vibrational energy levels,denoted by V0, V1, V2........Vn
i.e Between E1 and E2 there are V0, V1, V2........Vn vibrational energy levels. The difference between two vibrational levels goes on decreasing.

i.e(V1-V0)>(V2-V1)
 

Vibrational energy levels 

ROTATIONAL ENERGY LEVELS:-

Each vibrational energy levels are further divided into number of rotational energy levels, denoted by J1, J2, J3........ Jn.
The difference between two rotational energy levels goes on increasing.

i.e (J1-J0) <(J2-J1)

     (J2-J1) <(J3-J2)

Rotational energy levels