Perturbation of Molecular Rotation‐Vibration Energy Levels by Rare Gases

Abstract

The shift in frequency of lines of the 2–0 band of HCl and of the ν₁+ν₃ band of C₂H₂ due to the presence of krypton and xenon as foreign gases has been measured. A marked J dependence was observed. The relative shifts in the upper and lower states of the transitions were calculated from the shifts in the Δ₂F″(J) and Δ₂F′(J) values obtained from the measured line shifts. In the case of HCl the shifts in the rotational levels were markedly different in the upper and lower states, the upper state shift being proportional to J, while the lower‐state energy‐level shifts approach an asymptotic value for high J. For C₂H₂ the shifts in both levels resembled the shift in the lower state of HCl.