Objects Mixture Simulation Parameters <Prev Next>


If an external static field is included in the simulation then one or more of these can be added under the Simulation object as required, and describe the relative orientation of the static fields with respect to the absorbed or emitted radiation. If none are present random polarization is assumed. If no external field is present the object is ignored. See Transition Moments and Line Strengths for a note on how Spol values should be interpreted in the presence of a field.


Direction Select the polarization of the light, and thus the M selection rules. Possible values are:
  • Random - |ΔM | ≤ rank
  • Parallel - ΔM = 0
  • Perpendicular - ΔM = rank, rank−2, ... −rank
  • Circular - ΔM = +rank
(Rank = 1 for a normal single photon transition)

Note that PGOPHER versions before 8.0.186 also had a rank setting, and also relative intensities for random polarisation or rank ≠ 1 were not calculated correctly. Versions before 10.0.21 only included ΔM = ±rank transitions for Perpendicular transitions, which is correct for rank 1 but not for higher ranks. As part of the implementing this correctly a scale factor for parallel transitions for rank > 1 was also introduced (1/sqrt(6) for rank 2) which will affect absolute intensities.


Strength Relative strength of this component of the field - note that the relative intensity is proportional to the square of this value.