Hi friends and senior researchers,
While using the white light LED lamp and mercury vapor lamp of same intensity as a radiation source, the radiation impact on the sample shows variation. Therefore, kindly can we discuss the difference in radiation emitts by these sources?
Upendra Mahatme
Dear Upendra,
The main differences between LED lamps and Hg low-pressure discharge lamps, also known as fluorescent lamps (TL, PL, CFL, QL) are the emission spectrum and the power density (W/cm2). While the power density of a fluorescent lamp is typically in the range of 100 mW/cm2, modern phosphor converted InGaN LED can achieve a much higher power density up to 100 W/cm2.
The spectrum of fluorescent lamps comprise weak Hg lines at 365, 405, 436, 479, and 546 nm and the emission spectra of the phosphors, e.g BaMgAl10O17:Eu peaking at 453 nm, LaPO4:Ce,Tb at 544 nm and Y2O3:Eu at 611 nm. Such spectra are not continous due to the line emission of Tb3+ and Eu3+.
Spectra of phosphor converted LED comprise the emission band of the LED chip, emitting between 400 and 480 nm (depends on the manufacturer, Lumileds mostly use 465 nm), and the emission of the phosphors. While cool white LEDs comprise only a sinlge phosphor, mostly YAG:Ce, GdAG:Ce, or TAG:Ce, warm white LEDs also comprise a red emitting borad band phosphor, mostly (Ca,Sr)AlSiN3:Eu, O or (Ca,Sr,Ba)2Si5N8:Eu. In the past also (Ca,Sr)S:Eu was used. Also these phosphors deliver broad band emission due to the spin and parity allowed transitions of Eu2+ and Ce3+.
Hope this helps a bit! Otherwise please also check slide 17 of the attached presentation!
All the best
Thomas
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