Rhodamine 6G

We are trying several different dyes in our laser. The one we had in mind to use first is the dye Rhodamine 6G, also called Rhodamine 590 chloride. The formula of this dye is:

2-[6(ethylamino)-3-(ethylimino-2,7-dimethyl-3H-xanthen-9-yl]-benzoic acid, ethyl ester, chloride with a formula of: C₂₇H₂₉0₃N₂

The molecular structure is illustrated in Figure 5.

Figure 5. Rhodamine 6G.

The absorption maximum wavelength of Rhodamine 6G is 530 nanometers and the absorption range of the dye is 130 nanometers. The fluorescence emission maximum wavelength is 560 nanometers. The absorption and fluorescence spectrum of Rhodamine 6G is illustrated in Figure 3.

We have a few solvents to chose from in making the dye solution. However, the typical solvents are methanol, ethanol (with a dye concentration of 4.5 x 10^-5 M) or a methanol/water mixture (dye concentration 1 x 10^-4 M).

The Rhodamine needs to be pumped continuously from a reservoir. During the excitation of the dye, the heat produced by absorption of the pumping light by the dye solution strongly affects the system. It will produce changes in the density, and it can also produce changes in the fluorescence path and efficiency. We have decided to have one liter of this reservoir, and if we use the solvent ethanol the concentration of our dye will be 5 * 10^-5 mole/L. By using the equation :

5 * 10 ^-5 = ^x/_479.02
where x = 0.02395g

we can find out that we need 0.02g of Rhodamine 6G to make to the dye solution.

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