Measurement and simulation of O2(a1 Δg) density under low-pressure mercury lamp irradiation

The density of singlet delta oxygen O-2(a(1) Delta(g)) produced under low-pressure mercury lamp irradiation in an oxygen-nitrogen mixture is measured by infrared optical emission spectroscopy and compared with the results of simulations. A 30-cm-long lamp, whose radiation power is 1.9 W for 185 nm light and 12.2 W for 254 nm light, is irradiated in a cylindrical reactor of 8 cm inner diameter with an O-2(1-20%)/N-2 flow of 3.75-10 L/min. The measurement shows that the O-2(a(1) Delta(g)) density at the reactor outlet is approximately 1-2 ppm under all experimental conditions, regardless of the 02 concentration and the flow rate. The simulation reproduces the measurement results well and within an error of 50%. On the basis of the simulation model, the O-2(a(1) Delta(g)) density can be simply expressed as [O-2(a(1) Delta(g))] = 2.7 x 10(-3)I/(1 + 4.2 x 10(-4)[O-2]/[O-3]), where I is the illuminance at 254 nm. When [O-3]/[O-2] >> 4.2 x 10(-4), [O-2(a(1) Delta(g))] can be approximated as 2.7 x 10(-3)I, which is independent of parameters other than I, as shown by the measurement. The O-2(a(1) Delta(g)) densities calculated using these simple expressions agree with the measured O-2(a(1) Delta(g)) densities within an error of 80%. (C) 2015 Elsevier B.V. All rights reserved.