In this study, using laser induced fluorescence spectroscopy, effect of excitation wavelength on the fluorescence spectra of coumarin 4 in three different solvents has been studied. Excitation was done using third harmonic of Nd: YAG laser at 355 nm and 405 nm blue diode. Our results indicate that the fluorescence spectra of coumarin dye laser (7 - hydroxy -4 - methyl coumarin), unlike many of the dyes, is strongly dependent on the pump wavelength. Moreover, at a wavelength of 355 nm, the fluorescence shape of the solution will change as well. We attribute these results to specific chemical structure of the coumarin 4 solution.

Keywords: Laser induced fluorescence, excitation wavelength, coumarin 4

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