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## PowerPoint Slideshow about ' IR Spectroscopy' - lilka

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IR Spectroscopy

Wave length ~ 100 mm to 1 mm

Wave number ~ 100 to 10,000 cm-1

Frequency ~ 3 x 1012 to 3 x 1014 Hz

Energy ~ 1 kJ to 100 KJ /mole

HCl absorptions

- 2885.9 cm-1 fundamental band strong
- 5668.1 cm-1 first overtone weak
- 8347.0 cm-1 second overtone
- 10923.1 cm-1 third overtone
- 13396.0 cm-1 fourth overtone

Transition Moment Integral

Selection RuleMust have an oscillating dipole moment

Initial state

Final

state

Polyatomic molecules

Normal Modes

Center of mass does not move

Motion is in Phase

All atoms vibrate with same frequency

3N-6 Normal Modes

Bending mode of CO2 - 667 cm-1

We denote normal modes

as

Symmetric Stretch of CO2 1330 cm-1

Antisymmetric Stretching of CO2, 2349 cm-1

Vibrational energy of a polyatomic

Each Normal Modes = A Hamonic Oscillator

Energy of one hamonic Oscillator is known!

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