Principle of

Molecular Spectroscopy

Identification of an organic compound relied upon:elemental analysisphysical propertieschemical tests

Different spectroscopy techniques are used.study the interaction of emr with matterspectrometer spectrumultraviolet/visible (uv/vis),

infra-red (IR),nuclear magnetic resonance (nmr), mass spectrometry (MS)

Electromagnetic radiation can be described as a wave or as a particle.

As wave: λν = cAs a particle (photon): E=hν

Energy can be classified in different regions:

Probing different aspects of molecular structure:

Spectroscopic methods based on absorption of emr.

E1 ground state

E2 excited state

ΔE = hν energy

E1

E2

E3

E4

Energy

A spectrum

electronic energy level 1

Ener

gy electronic energy level 2

vibrational energy level

rotational energy levels

A molecule in space can have many sorts of energy.