Photolysis of rhodamine-WT dye

Photolysis of rhodamine-WT dye under natural sunlight conditions was determined by measuring the loss of fluorescence as a function of time. Rate coefficients at 30° north latitude ranged from 4.77 × 10⁻² day⁻¹ for summer to 3.16 × 10⁻² day⁻² for winter. Experimental coefficients were in good agreement with values calculated using a laboratory-determined value of the quantum yield.