VIBRATIONAL SPECTROSCOPY

Intermolecular H-bonding Gives

• Broader bands

• Sharp bands

THE NUMBER OF VIBRATIONAL DEGREE OF FREEDOM OF CO2 MOLECULE IS

• 3

• 5

• 6

• 4

THE MOLECULE WHICH IS IR INACTIVE IS

• N₂

• HCl

• O₂

• BOTH N₂ &O₂

THE ABSORPTION OF IR RADIATION IS ACCOMPANIED BY TRANSITIONS INVOLVING

• ROTATIONAL LEVEL

• VIBRATIONAL LEVEL

• ELECTRONIC LEVEL

• NUCLEAR SPIN LEVEL

SELECTION RULE FOR VIBRATIONAL SPECTROSCOPY-SHO

• _{DJ =±1}

• Dn =±1,

• DJ =0

• Dn =0

I R SPECTRA OBSERVED IN

• VISIBLE REGION

• X-RAY REGION

• UV REGION

• MID AND NEAR IR REGION

CONDITION FOR THE MOLECULE TO BE IR ACTIVE

• PERMANENT DIPOLE MOMENT

• CHANGE IN POLARSIBILITY

• CHANGE IN DIPOLE MOMENT

• NONE

IR SPECTRUM OBSERVED INTHE WAVELENGTH RANGE

• 10 -100 cm

• 100-1000cm

• 10-3 -10-5 cm

• 1 -1000 cm

For a transition taking place from n to n +1, the vibrational frequency is given by

• ⍵_{OSC cm}^-1

• 1/⍵_OSCcm^-1

• 1+1/⍵_OSCcm^-1

• 1+⍵_{OSC cm}^-1

FUNDAMENTAL TRANSITION IS GIVEN BY

• =2⍵e(1-2 xe) cm-1

• =⍵e(1+2 xe) cm-1

• =⍵e(1-2 xe) cm-1

• =3⍵e(1-2 xe) cm-1