How does ultraviolet light produce ozone?
Release time:2020-12-30 13:52
Number of Views:1062
Theoretically, the photon energy higher than the bond energy can break the chemical bond. Therefore, ultraviolet light with wavelength shorter than 243 nm can stimulate oxygen in air or water to produce ozone. Uvc-led with wavelength higher than 243 nm does not produce ozone.
Low pressure mercury lamp will produce ozone, because the vapor pressure is 1.3 ~ 13P, and there is 185nm vacuum ultraviolet in the luminescence spectrum of low pressure mercury lamp. This ultraviolet light will stimulate oxygen in the air to produce a combination reaction, which turns into ozone. In essence, ultraviolet breaks the covalent bond between oxygen and oxygen, and then combines with oxygen to form O3. Uvc-led will not produce ozone, because the covalent bond energy of oxygen and oxygen is as high as 5.1ev, which requires ultraviolet light with a wavelength at least shorter than 243nm to break and finally generate ozone.
2. Why doesn't led produce ozone?
Low pressure mercury lamp can improve the energy level transition probability of short wave ultraviolet by controlling vapor pressure, but it will be accompanied by other transitions, mainly 254 nm and 185 nm. The first level transition probability of uvc-led is dominant, so the luminescence is pure. The wavelength of common uvc-led is higher than 255 nm.
Low pressure mercury lamp is a kind of gas light source, and its excited state energy level position has been determined by mercury. Therefore, although there are high pressure, medium pressure and low pressure mercury lamps, the difference of vapor pressure only regulates the probability of transition between different excited states, that is, the relative intensity of different characteristic peaks. Therefore, the low-pressure mercury lamp mainly emits 254 nm and 185nm light. As a kind of AlGaN semiconductor light-emitting diode with quantum well structure, uvc-led is dominated by E0 transition, with only one peak wavelength, such as 275nm. It can be found that the FWHM of the main peak of deep UV LED is significantly lower than that of blue light, which is also because the electronic transition of quantum well light-emitting device is more single than that of multi size quantum dot light-emitting device. Because the emission wavelength of mass-produced uvc-led is not lower than 243nm, the deep UV uvc-led for sterilization does not produce ozone.
Low pressure mercury lamp will produce ozone, because the vapor pressure is 1.3 ~ 13P, and there is 185nm vacuum ultraviolet in the luminescence spectrum of low pressure mercury lamp. This ultraviolet light will stimulate oxygen in the air to produce a combination reaction, which turns into ozone. In essence, ultraviolet breaks the covalent bond between oxygen and oxygen, and then combines with oxygen to form O3. Uvc-led will not produce ozone, because the covalent bond energy of oxygen and oxygen is as high as 5.1ev, which requires ultraviolet light with a wavelength at least shorter than 243nm to break and finally generate ozone.
2. Why doesn't led produce ozone?
Low pressure mercury lamp can improve the energy level transition probability of short wave ultraviolet by controlling vapor pressure, but it will be accompanied by other transitions, mainly 254 nm and 185 nm. The first level transition probability of uvc-led is dominant, so the luminescence is pure. The wavelength of common uvc-led is higher than 255 nm.
Low pressure mercury lamp is a kind of gas light source, and its excited state energy level position has been determined by mercury. Therefore, although there are high pressure, medium pressure and low pressure mercury lamps, the difference of vapor pressure only regulates the probability of transition between different excited states, that is, the relative intensity of different characteristic peaks. Therefore, the low-pressure mercury lamp mainly emits 254 nm and 185nm light. As a kind of AlGaN semiconductor light-emitting diode with quantum well structure, uvc-led is dominated by E0 transition, with only one peak wavelength, such as 275nm. It can be found that the FWHM of the main peak of deep UV LED is significantly lower than that of blue light, which is also because the electronic transition of quantum well light-emitting device is more single than that of multi size quantum dot light-emitting device. Because the emission wavelength of mass-produced uvc-led is not lower than 243nm, the deep UV uvc-led for sterilization does not produce ozone.
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