vibrational spectroscopy che 626 alex nazarenko [email protected]
Post on 20-Dec-2015
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Width
Dopplerc
v
Speed of light 300,000,000 m/s
Velocity of a particle >1000 m/s
collisions Approximately as Doppler
Both effects increase with the temperature and
decrease with the size of the molecule/atom
Multiple energy levels
Width is around 0.01-0.001 nm in visible area
Raman scattering
Escaping photon has smaller energy because the molecule did not return to the ground state
E The identity transformation (E coming from the German Einheit, meaning unity).
CnRotation (clockwise) through an angle of 2π/n radians, where n is an integer. The axis for which n is greatest is termed the principal axis.
Cnk Rotation (clockwise) through an angle of 2kπ/n radians. Both n and k are integers.
Sn
An improper rotation (clockwise) through an angle of 2π/n radians. Improper rotations are regular rotations followed by a reflection in the plane perpendicular to the axis of rotation. Also known as alternating axis of symmetry and rotation-reflection axis.
i
The inversion operator (the same as S2). In Cartesian coordinates, (x, y, z)→(−x, −y, −z). Irreducible representations that are even under this symmetry operation are usually denoted with the subscript g for gerade (german=even), and those that are odd are denoted with the subscript u for ungerade (german=odd).
σ A mirror plane (from the German word for mirror - Spiegel).
σhHorizontal reflection plane - passing through the origin and perpendicular to the axis with the ‘highest’ symmetry.
σvVertical reflection plane - passing through the origin and the axis with the ‘highest’ symmetry.
σd
Diagonal or dihedral reflection in a plane through the origin and the axis with the ‘highest’ symmetry, but also bisecting the angle between the twofold axes perpendicular to the symmetry axis. This is actually a special case of σv.