Showing papers by "James B. Burkholder published in 2006"
TL;DR: It is concluded that these compounds are acceptable substitutes for CFCs in terms of their impact on Earth's climate.
Abstract: Rate coefficients for reaction of the hydroxyl radical (OH) with three hydrofluorocarbons (HFCs) CF3CH2CH3, HFC-263fb, (k1); CF3CHFCH2F, HFC-245eb, (k2); and CHF2CHFCHF2, HFC-245ea, (k3); which are suggested as potential substitutes to chlorofluorocarbons (CFCs), were measured using pulsed laser photolysis−laser-induced fluorescence (PLP−LIF) between 235 and 375 K The Arrhenius expressions obtained are k1(T) = (436 ± 072) × 10-12 exp[−(1290 ± 40)/T] cm3 molecule-1 s-1; k2(T) = (123 ± 018) × 10-12 exp[−(1250 ± 40)/T] cm3 molecule-1 s-1; k3(T) = (191 ± 042) × 10-12 exp[−(1375 ± 100)/T] cm3 molecule-1 s-1 The quoted uncertainties are 95% confidence limits and include estimated systematic errors The present results are discussed and compared with rate coefficients available in the literature Our results are also compared with those calculated using structure activity relationships (SAR) for fluorinated compounds The IR absorption cross-sections at room temperature for these compounds were measured
24 citations
TL;DR: The peak cross section of the P(8) line was determined to be (1.98 ± 0.36) × 10−18 cm2, and the intensity of the entire band was normalized to this line as mentioned in this paper.
Abstract: Absorption cross sections for the A
2A″ (0,90,0) ←
2A′ (0,01,0) band of HCO were determined at 295 K using pulsed laser photolysis combined with cavity ring-down spectroscopy. Formyl radicals (HCO) were produced from the reaction of atomic chlorine, generated by photolysis of Cl2 at 335 nm, with formaldehyde. The concentration of HCO was calibrated using two independent photochemical methods. The peak cross section of the P(8) line was determined to be (1.98 ± 0.36) × 10−18 cm2, and the intensity of the entire band was normalized to this line. The quoted 2σ uncertainty includes estimated systematic errors. Comparisons to previously reported values of HCO cross sections in this band are discussed.
23 citations