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Laser Physics I PH581-VTA (Mirov)

Molecular Gas Lasers I

Lectures 23-24 chapter 9

Fall 2017C. Davis, “Lasers and Electro-optics”

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Molecular Structure: Diatomic Molecules

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CO

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Vibrational Structure

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Vibrational – Rotational Transitions

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+1

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Electronic States in Molecules. Notation.

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Term symbols of diatomic moleculesthe symmetries and parities are different between a heteronuclear diatomic and a homonuclear one. Their term symbols usually have different formats. For homonuclear diatomics, the term symbol has the following form:

2S+1Λ(+/−)Ω,(g/u)

whereas Λ is the projection of the orbital angular momentum along the internuclear axis: Ω is the projection of the total angular momentum along the internuclear axis; g/u is the parity; and +/− is the reflection symmetry along an arbitrary plane containing the internuclear axis. Λ may be one of the greek letters in the sequence: Σ Π Δ Φ... when Λ = 0, 1, 2, 3..., respectively. For heteronuclear diatomics, the term symbol does not include the g/u part, for there is not inversion center in the molecule.

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Franck-Condon Principle

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Molecular gas lasers.The energy levels of molecule – electronic, vibrational and rotational.

Electronic energy states.

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Vibrational Energy States

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Vibrations of polyatomic molecules

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Rotational Energy States

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CO2 Lasers

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The Carbon Monoxide Laser