A NEW METHOD FOR DIRECT MEASUREMENT OF SPECTRAL LINE STRENGTHS AND WIDTHS,

The most important sources of error incurred in the measurement of spectral line parameters arise from uncertainty in the determination of the 100 transmittance, the distortion of the line profile by the spectrometer, and from lack of knowledge of the true shape of the spectral line. These errors have been investigated numerically by passing an idealized spectrometer slit function over various assumed line profiles. Families of correction curves have been constructed in this manner from which spectral line strengths, widths, and peak absorption coefficients may be determined from apparent values measured directly from the chart recorder. The effect of the form of the slit function has been investigated by using triangular, Gauss, Cauchy, and combination Gauss-Cauchy slit functions. The effect of uncertainties in the line shape has been investigated by using Gauss, Lorentz, and modified Lorentz line shapes. The correction procedure has been applied to the self- and nitrogen-broadened R0 and R1 lines in the first overtone band of hydrogen fluoride. The measurements were made on collision-broadened lines near the linear region of growth, and within experimental error the line parameters were found to obey the Lorentz relation. The measured self-broadened line widths indicate a non-Lorentz behavior in that they do not vary linearly with pressure. When broadened by nitrogen, the line widths follow the expected linear dependence on pressure well within experimental error. Author