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A sample is placed in an oscillating electric field (F) and light (E) is passed through it to a detector. The change in absorption (relative to the case when F = 0) is recorded as a function of the angle between the fields, c. The experiment then yields information about the change in polarizability (Da) and the change in dipole moment (Dm) between ground and excited states. |
| The electric field perturbs the absorption band in a way that produces Stark signals looking like derivatives (zeroth, first, and second) of the original absorption spectrum. In the figure above, the black lines indicate the original (F = 0) spectrum, and the red and blue lines indicate the effect of the electric field. The resulting Stark signal is then a linear combination of the zeroth, first, and second derivative components. |  |