VUV emission by XeI excimer in Low-Pressure Xenon-Iodine mixture

In these days, the damage of hot springs quality by bacilli is getting serious problem. The bacilli can be killed out by heating, chlorination or ultraviolet rays irradiation in general. However, some of bacilli have the tolerance in heat and chlorine, on the other hand they do not have the tolerance in ultraviolet rays. Therefore, most bacilli can be killed out by using ultraviolet rays (Yoshino, 2004). The wavelength of effective ultraviolet rays for sterilization is in the vicinity of 250 nm. Mercury has a spectrum with strong resonance wavelength 253.7 nm. Therefore, mercury is used for the ultraviolet source. However, there are strong needs to reduce harmful mercury, because mercury can cause environmental problems. Then, the authors have paid attention to XeI emitting the radiation of 253 nm, which is near resonance radiation (253.7 nm) of mercury. In this study, the authors investigated the characteristics of the ultraviolet-rays light source that used XeI. Dielectric barrier discharge (DBD) is used as a lighting method. Parameter of xenon filling pressure was 39.9 Pa or 1.33 kPa. The vapor pressure of the iodine in the discharge tube was assumed to be 46.6 Pa from the temperature of the discharge tube wall. Two aluminum tapes (60 mm long and 20 mm wide) have been set in the opposite position of the outer wall of a discharge tube to each other as external electrodes. And the sinusoidal wave voltage or the pulsed negative voltage was impressed to the external electrode. By the dielectric barrier discharge, XeI excimers were generated and radiation around 253 nm from XeI was obtained. Consequently, when the partial pressure of the xenon was low, the continuous spectrum (peak wavelength 342 nm) from the iodine molecule was strongly radiated. However, when the partial pressure of the xenon was high, the continuous spectrum (peak wavelength 253 nm) from XeI was strongly radiated