Peter Spietz

Iodine and mercury resonance lamps for kinetics experiments and their spectra in the far ultraviolet

Electrodeless iodine and mercury iodide radio-frequency discharge lamps have been made to provide intense sources of resonance radiation of iodine and mercury in the 183-253 nm region. Production technology and emission spectra in the ultraviolet and vacuum ultraviolet regions are described. Both lamps (iodine and mercury iodide) are designed and used for monitoring the iodine 2P1/2 (206.163 nm) and 2P3/2 (183.038 nm) level population kinetics after flash photolysis of I2 or other precursor molecules in laboratory experiments. The technique is suitable for the investigation of the gas phase reaction kinetics following the photolysis of I2 in the presence of O3.

Estimation of the emission temperature of an electrodeless discharge lamp and determination of the oscillator strength for the I(2P3/2) 183.038 nm resonance transition

Ž2 . The 183.038 nm resonance absorption transition of I P has been studied using a flash photolysis set-up for 3 2 gas-phase chemistry and a radio frequency powered electrodeless discharge lamp filled with iodine. The dependence of self-absorption and self-reversal on iodine partial pressure in the discharge volume was measured. The optimum iodine partial pressure, with self-absorption minimized and acceptable intensity, is determined to be approximately 2.5 10 3 mbar. A method is described to estimate the temperature of the emitting atoms using direct measurements of relative absorption at different absorber concentrations. This yields an emission temperature of 923 50 K. Ž2 . Using this temperature, the oscillator strength for the I P transition at 183.038 nm is determined to be 3 2 Ž . 3 Ž . f 3.87 0.57 10 , corresponding to an absorption cross-section at the center of the line of 5.42 0.8 10 14 cm2 atom 1 This shows a difference from one of two earlier measurements, but is close to the other. The . remaining difference from the latter measurement is probably due to tendencies of opposite biases inherent to the experiments. 2001 Elsevier Science B.V. All rights reserved. Ž2 .

Iodine and bromine resonance lamps in atmospheric research

For the first time previously developed iodine resonance spectra source has been tested in flash photolysis experiment. Quantitative measurements of concentration kinetics of iodine atomic species in a I2+O3 system are possible. The 183.038 nm resonance absorption transition of I(2P3/2) in previously developed EDL has been studied; dependence of self-absorption and self-reversal on iodine partial pressure in the discharge volume has been measured. The search for optimal conditions for an iodine EDL with minimized self-absorption and sufficient intensity were made. In condition of flash photolysis with previously described method it is possible to determine the emission temperature, oscillator strength and corresponding absorption cross section for the I(2P3/2) transition at 183.038 nm. With special set-up shown here it is possible to use the continuous light sources for absorption spectroscopy of molecular iodine species together with atomic iodine line soruce for resonance absorption spectroscopy of atomic iodine sepcies. There are evidences that bromine sources could be used in similar ways.