Cavity Ring-down Laser Spectroscopy Research Articles

Novel dose rate monitoring for intense radiation fields based on cavity ring-down laser spectroscopy

To monitor dose rates in intense radiation fields, we are developing a novel dose rate monitoring method based on cavity ring-down laser absorption spectroscopy, where the dose rate of the radiation field can be derived from concentrations of the radiation induced chemical species in irradiated gas. We have attempted to verify the operational principle of this method through off-line/on-line measurements of /sup 60/Co gamma-ray induced O/sub 3/ and NO/sub 2/ in air. The results of these experiments demonstrated that the present method is quite useful for dose rate monitoring in intense radiation fields with high radiation resistance, by showing the detectable range of an absorbed dose rate from 0.5 to 2000 Gy/s with a time resolution of about 30 s.

Reactions of Cl Atoms with Dimethyl Sulfide: A Theoretical Calculation and an Experimental Study with Cavity Ring-Down Spectroscopy

The adduct formation in the reactions of Cl and Br atom with dimethyl sulfide (DMS) is studied theoretically and experimentally. The rate constants of the forward reaction at several temperatures and pressures are determined from the rise and decay time profiles of the adduct, Cl−DMS, using cavity ring-down laser spectroscopy. The high-pressure limit rate constant for the Cl−DMS adduct formation is determined to be k1a(high) = (2.2 ± 0.2) × 10-10 cm3 molecule-1 s-1. The rate constant of Cl with DMS at atmospheric pressure is k1 = (3.6 ± 0.2) × 10-10 cm3 molecule-1 s-1. Error bars are 1σ. The Arrhenius plot of the forward reaction has a negative temperature dependence for 278−318 K. The calculated equilibrium constants of the reaction Cl and Br with DMS at 300 K are KClDMS = 2.8 × 10-12 and KBrDMS = 7.7 × 10-15 cm3 molecule-1, respectively. The binding energy (D0) is calculated to be 17.7 kcal mol-1 for Cl−DMS, and 14.1 kcal mol-1 for Br−DMS. D0(Br−C) is in fair agreement with the previously reported exper...

Temperature and Pressure Dependence Study of the Reaction of IO Radicals with Dimethyl Sulfide by Cavity Ring-Down Laser Spectroscopy

The reaction of IO radicals with dimethyl sulfide was studied using cavity ring-down laser spectroscopy. The reaction rate constant shows both a temperature and pressure dependence. At 100 Torr total pressure, the reaction has reached its high-pressure limit and has a rate constant of (2.5 ± 0.2) × 10-13 molecule-1 cm3 s-1 at 298 K. On the basis of the Arrhenius plot in the region of 273−312 K, the reaction has a negative activation energy (Ea = −18.5 ± 3.8 kJ mol-1). The atmospheric implications of these findings are discussed. In light of these new data, DMS oxidation by IO can compete with oxidation by the hydroxyl radical in the marine boundary layer. Quoted uncertainties are one standard deviation from regression analysis.