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I am trying to understand the electronic structure of the negatively charged NV centre in diamond, where there is a so-called Zero-Phonon Line (ZPL) in the spectrum. Can anybody explain what a ZPL is?

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up vote 4 down vote accepted

The zero phonon line is the wavelength at which an excitation/relaxation is not phonon assisted.

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What is it assisted by in that case? – DanielSank Feb 4 '15 at 8:50
Photon absorption, where the wavelength of the photon corresponds to the exact energy level splitting of the ground and optically excited state. – Angelo Feb 11 '15 at 9:48
Oh, right, of course. – DanielSank Feb 11 '15 at 16:46

You should research the configuration-coordinate diagram first. The Zero phonon line (ZPL) is the energy difference between the excited state and ground state.

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Welcome to Physics.SE! This is rather brief for the answers we would like on the site. Could you elaborate some more? – Emilio Pisanty May 5 '14 at 14:35

for each defect level, the energy value was not constant. If atom configuration relaxed, value would change into parabolic curve.

As mentioned by upper user, ZPL was the difference between the lowest values of excited state and ground state.

And ZPL line have a distinct peak in experimental spectrum.

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