Raman Spectra

Raman transitions must currently be specified using Spherical tensor notation (like multiphoton transitions). Normal Raman spectroscopy uses two photons, and can give rise to Rank 0, 1 (often weak) and 2 contributions to the overall transition moment. You may need more than one of these to simulate a transition, and for each Rank, k, there will be 2k+1 components from -k to +k. PGOPHER labels these as T(Rank, Component). For a linear molecule the following components might be expected to contribute:
Σ-Σ T(0,0) (normally dominant) and T(2,0)
Σ-Π T(2,1)
Π-Π T(0,0) (normally dominant), T(2,0) and T(2,2)
Σ-Δ T(2,2)