Abstract
The fundamental low frequency parallel band at and its upper stage band at have been re-examined under high dispersion. It is found that most of the fine structure lines hitherto reported as single are resolved into multiplets. The positions of the lines may be accounted for accurately by assuming that the energy levels have the form, The superscripts or indicate whether the level in question is the lower or the upper of the two levels produced by the double minimum potential. is the small centrifugal distortion term calculated by Slawsky and Dennison. The constants , , , , , and are determined from the experimental data. The following vibrational energies are also found, , and .
In the discussion of the rotational constants, it is pointed out that two quantities are involved, (a) the average constants, averaged over the two levels of the double minimum, as , and (b) the difference of the constants, as . Recently Shaffer has calculated the theoretical expressions for the averaged constants and has shown how these depend upon the anharmonic terms in the potential energy. A treatment of the difference of the constants is equivalent to a treatment of the change in the splitting of the two levels of the double minimum due to the vibration-rotation interaction. This may be computed from the expression for the splitting of the double minimum levels given by the W-K-B method of approximation. The calculated result for the change in splitting of the first vibration levels is which is in excellent agreement with the observed change The significance of the agreement is discussed.
- Received 9 October 1941
DOI:https://doi.org/10.1103/PhysRev.60.786
©1941 American Physical Society