Graph 2: Fluorescent Emissions Caused by One- and Two-Photon Excitations

Graph 2 is a Cadmium selenide (CdSe) nanocrystal spectra. (a) corresponds to two-photon excited fluorescence spectrum; (b) the the fluorescence spectrum caused by one-photon excitation. (c) and (d) are the curves of the two-photon and one-photon exci tation spectra, respectively. By comparing the energy of fluorescent light emission caused by one- and two-photon excitations the researchers could estimate the magnitude of the dipole moment. The peaks in curves (b) and (d) coincide with the shoulders in curves (a) and (c). These shoulders should not be present if the nanocrystal has a simple spherical structure. A dipole moment in the nanocrystal would account for the shoulders.

*Graph 2 adapted from:

"Polar CdSe Nanocrystals: Implications for Electronic Structure"
Mark E. Schmidt, Sean A. Blanton, Margaret A. Hines, and Philippe Guyot-Sionnest, J. Chem. Phys. 106, 5254-5259 (March 22, 1997).

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