Quantitative absorption spectroscopy of residual water vapor in high-purity gases: pressure broadening of the 1.39253-um H_2O transition by N_2,HCI,HBr,CI_2,and O_2

摘要

We determined the respective pressure-broadening coefficients of HCl, HBr, Cl_2, and O_2 (expressedrelative to that of the reference gas N_2) for the (v_1,v_2,v_3)J_(Ka,Kc) = (0,0,0)3_(0,3) -> (1,0,1)2_(0,2) rovibrational tyansition of H_2 16~O that occurs at 1.39253 um. The experiment used a continuous-wave cavity ring-down spectyoscopy analyzer to measure the peak absorption losses as a function of added moisture concentration. The measured pressure-broadening coefficients for HCl, HBr, Cl_2, and O_2 are, respectively, 2.76, 2.48, 1.39, and 0.49 times that of the N_2 pressure-broadening coefficient, and detection limits for water vapor range from 0.22 nmol mol~-1 for O_2 matrix gas to 2.3 nmol mol~-1 for HBr matrix gas. The degradation of the detection limit (relative to the N_2 matrix gas) is ascribed to a pressure-broadening-induced reduction in peak absorption cross section and to elevated background loss from the matrix gas.