I'm reading an article about two-dimensional infrared spectroscopy and I don't understand the following sentence.
Bleach or stimulated emission contributions yield negative signals.
What are "bleach contributions"? I have never heard of it and cannot find a suitable explanation on the Internet. Can somebody explain that to me?
The article I'm referring to is J. Chem. Phys. 121, 5935 (2004)
Answer
I feel obliged to post another answer since the first one contains a mistake.
As you deplete the ground state, you also populate the excited state, and when the photon interacts with the excited molecule, then instead of being absorbed it generates another photon through stimulated emission. The paper you cite treats this contribution as a negative signal.
Eventually, at 50/50 population you reach an equilibrium, where the amount of absorbed light is equal to the amount of light produced by stimulated emission, and it looks like your medium is not absorbing light at all, which is why it is called bleaching (i.e. loosing its color).
No comments:
Post a Comment