Measurements of Pressure-Broadening Coefficients for the F‘ = 3 ← F‘ ‘ = 4 Hyperfine Line of the ²P_1/2 ← ²P_3/2 Transition in Atomic Iodine

Abstract

We describe a series of measurements of pressure-broadening coefficients for the F′ ) 3 r F′′ ) 4 line of the 2 P 1/2 r 2 P 3/2 transition in atomic iodine. This is the optical transition of the chemically pumped atomic iodine laser (COIL), and our results are relevant to a more complete understanding of this important class of high-power lasers. The measurements were made in sealed cells using an argon ion laser to photodissociate molecular iodine and a tunable diode laser to probe directly the atomic transition. We measured broadening coefficients for three bath gases: He, N 2 , and O 2 . Full absorption line shapes were recorded as a function of the added bath gas pressure and the following values were obtained at room temperature: (∆ν/∆P He ) T)296K ) 3.2 ( 0.3 MHz/Torr, (∆ν/∆P N2 ) T)296K ) 5.5 ( 0.6 MHz/Torr, and (∆ν/∆P O2 ) T)296K ) 5.0 ( 0.5 MHz/ Torr; where ∆ν is the full width at half-maximum. We also measured the temperature dependencies of the He and O 2 broadening coefficients over the range 296 K < T < 775 K. We quote the temperature-dependent values as (∆ν/∆P He ) T ) (3.2 ( 0.3) × (296/T) 0.36 and (∆ν/∆P O2 ) T ) (5.5 ( 0.6) × (296/T) 0.70 . Comparisons to previous measurements are also discussed. † Part of the special issue "Donald Setser Festschrift".

Ultraviolet photochemistry of trichlorovinylsilane and allyltrichlorosilane: vinyl radical (HCCH2) and allyl radical (H2CCHCH2) production in 193 nm photolysis

“…The iodine absorption cross section used is corrected for the small amount of collisional broadening by using known broadening coefficients for He and O 2 . 28 The gases were delivered by calibrated mass flow controllers. The excimer laser dissociates approximately 10 À3 of the photolyte each shot, and the entire cell volume was refreshed every 4-5 shots at the 1 Hz repetition rate of the experiments.…”

Buffer-gas pressure broadening for the (3 001)III← (0 0 0) band of CO2measured with continuous-wave cavity ring-down spectroscopy

“…For the line broadening of atomic iodine with He and O 2 at 296 K o T o 775 K, Davis et al reported n(He) ¼ 0.36 and n(O 2 ) ¼ 0.70 24. …”

Measurements and Modeling of HO2Formation in the Reactions ofn-C3H7andi-C3H7Radicals with O2

“…Comparison of the predicted (solid and dashed curves) and observed (circles) (a) HO2 (every 50th point shown for clarity) and (b) I (every 100th point shown) produced in the photodissociation of n-propyl iodide at 648 K obtained by infrared FM spectroscopy.The solid curve is obtained by using the present kinetic model (as depicted in Figures4 and 5), and the dashed curve is obtained by increasing the rate coefficients for I + RO 2 and I + HO2 by factors of 10 and 3, respectively. Observed I-atom concentrations are derived by using the absolute absorption cross section for the F* ) 3 r F ) 4 hyperfine transition of iodine atoms at 1.315 µm 39,40.…”