We determined the respective pressure-broadening coefficients of HCl, HBr, Cl2, and O2 (expressed relative to that of the reference gas N2) for the (nu1,nu2,nu3)J_Ka,Kc = (0,0,0)3_0,3 --> (1,0,1)2_0,2 rovibrational transition of H2 ^16O that occurs at 1.39253 µm. The experiment used a continuous-wave cavity ring-down spectroscopy analyzer to measure the peak absorption losses as a function of added moisture concentration. The measured pressure-broadening coefficients for HCl, HBr, Cl2, and O2 are, respectively, 2.76, 2.48, 1.39, and 0.49 times that of the N2 pressure-broadening coefficient, and detection limits for water vapor range from 0.22 nmol mol^-1 for O2 matrix gas to 2.3 nmol mol^-1 for HBr matrix gas. The degradation of the detection limit (relative to the N2 matrix gas) is ascribed to a pressure-broadening-induced reduction in peak absorption cross section and to elevated background loss from the matrix gas.
© 2005 Optical Society of America
Vasil Vorsa, Seksan Dheandhanoo, Suhas N. Ketkar, and Joseph T. Hodges, "Quantitative Absorption Spectroscopy of Residual Water Vapor in High-Purity Gases: Pressure Broadening of the 1.39253-µm H2O Transition by N2, HCl, HBr, Cl2, and O2," Appl. Opt. 44, 611-619 (2005)