We determined the respective pressure-broadening coefficients of HCl, HBr, Cl2, and O2 (expressed relative to that of the reference gas N2) for the (ν1,ν2,ν3)JKa,Kc = (0,0,0)30,3 → (1,0,1)20,2 rovibrational transition of H216O 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
Original Manuscript: May 13, 2004
Revised Manuscript: August 23, 2004
Manuscript Accepted: August 25, 2004
Published: February 1, 2005
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)