IR spectroscopy (infrared spectroscopy ) pdf

IR spectroscopy :-
                               Introduction :-                                                                                  The molecule which contain permanent dipole moment or genrate dipole moment during the vibration is called IR active molecule.

Selection rule for IR spectroscopy :-

                                                            As we know IR spectrum arrives due to the various transition the simple vibration of a molecule can be considered as simple harmonic oscillator  (SHO) but the real is unhormonic in nature so the selection rule can be written as.

In IR spectroscopy we consider a molecule has unhormonic oscillator and explain the various types of band arrises in the spectrum.
👉Type of band in IR spectroscopy :-
                                                               The selection rule of unhormonic oscillator can be written as.

The real molecule show vibrational transition according to the given selection rule and we observed various bands in IR spectra.
1.Fundamental band:-
                                    At normal conditions most of the molecule exist in v=0 level so initially transition start from V=0 level
The band which arrises due to the transition between v=0 to v=1 is called fundamental band each very high because the probability of transition from v=0 to v=1 is also very high
2. Over tone band:-
                                   The multiple peak of band is called overtone
If v=+2 (first overtone band )
If v=+3 (second overtone band )
If v=+4 (third overtone band  )
3. Hot band :-
                        The band which arrieses  due to the transition from V=1 to v=2 is known hot band.
These band appear in the spectrum particularly at high temperatures that why they are called hot band .
Hot band is also secondary fundamental band.
The intensity fundamental band is high as campare to other band.