# Nonlinear and Two-Dimensional Spectroscopy (Tokmakoff)

- By: Andrei Tokmakoff
- Publisher: University of Chicago
- Source: [LibreTexts](https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Nonlinear_and_Two-Dimensional_Spectroscopy_(Tokmakoff))
- Licence: [CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/)
- Read at LibreTexts: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Nonlinear_and_Two-Dimensional_Spectroscopy_(Tokmakoff)
- PDF: https://downloads.libretexts.org/api/v1/download/chem-290631/pdf

Different spectroscopies give you different perspectives. Linear spectroscopy commonly refers to light-matter interaction with one primary incident radiation field which is weak, and can be treated as a linear response between the incident light and the matter. From a quantum mechanical view of the light field, it is often conceived as a “one photon in/one photon out” measurement. Nonlinear spectroscopy is used to refer to cases that fall outside this view.