Confirming Sγ products by blending isotopic doublets of HCl

Experimental confirmation is reported of a published technique, ⁽²⁾ applicable to the square root region which specifies the degree to which two Lorentz absorption lines, not necessarily equal, overlap. It also specifies the deficiency, γ, of the aggregate equivalent width of the blend from its value when the two lines are completely independent. The experiment was conducted at room temperature using pure HCl gas in a 3·34 m path at pressures from 2 to 750 torr. It consisted of sequentially pressure blending fundamental band isotopic doublets. The blended equivalent width of each doublet was compared to predictions from the aforementioned theory as a function of pressure, using previously published values of S and γ as the basis for its application.Published line strength values for the HCl fundamental band agree well only in the upper R (J≥7) branch. These were used to test the procedure. Predictions based upon divergent line strengths in the remainder of the band were then compared to the experimental results and confirm the accuracy of the Sγ products of Benedictet al.⁽¹⁾A polynomial representation of the Ladenburg-Reiche function is given which is useful in extending the procedure of Ref. (2) to the linear region.Finally, a new experiment is described, based upon the confirmed theory, which allows the validity of the Lorentz shape to be assessed as a function of pressure for various foreign broadeners and interaction potentials. Application to cometary abundance determinations is also discussed.