a. Raman-cross-section s -- intrinsic strength of the oscillating dipole of the target mineral
b. the number of molecules within the volume irradiated by the laser beam --volume to surface ratio, porosity, grain size, and mixed grain sizes
c. internal heterogeneity within a mineral grain, fractures, chemical zoning, and vitrification |
a. Multiple reflections of the excitation laser beam -- penetration depth
b. Multiple internal reflections of the scattered Raman signal -- collection volume
Causes are target surface relief, grain boundaries within the irradiated volume, and changes of index of refraction caused by chemical or structural heterogeneity within a mineral grain. |