Line Strengths and Widths in Hydrogen Iodide

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Abstract
Measurements on 13 lines in the hydrogen iodide fundamental vibration—rotation band have yielded a set of line strengths of considerable accuracy. From these strengths a total band intensity of 0.37 cm—2 atm—1 at 300°K has been computed, as well as a value for the vibration—rotation interaction parameter θ which is found to be —5. Both of these figures indicate that the ``effective charge'' of this molecule is remarkably small, which fact is reflected in a great dominance of the R branch over the P branch. Using the line strengths as input data, linewidths have been computed from equivalent width measurements. Finally, the linewidths have been converted to optical collision cross sections. The J dependence of the linewidths and the collision cross sections is not typified by the other hydrogen halides. The usual resonance peak is absent and a lower limiting value seems to be reached by | m |=3. Furthermore, the collision cross sections for the lines of higher J are much larger than might be inferred from the other hydrogen halides.