Knowledge Bank

“New observations1 on $N14O216$ have yielded precise frequencies for the six strong and four weak lines with $\Delta F-\Delta N$ of the rotational transition $919⟶100,10$ near 41 Kmc. The six strong lines of the transition $221,21⟶212,30$ have also been measured. As expected, combination rules govern some of the frequencies of the $919⟶100,10$ transition. The microwave spectrum of $N15O216$ is calculated to be blank from 5 Kme to 50 Kme, except for lines with $N>35$. The transition $919⟶100,10$ was predicted near 52 Kme, and four lines have now been measured in this region. These are presumably the four strong lines with $\Delta F=\Delta N$ of $919⟶100,10$ of $N15O216$. An improbable assignment not yet rigorously excluded would attribute these to a magnetic dipole transition of $N14O216$. Sufficient data are now available to test the theory developed by $Lin2$ for an accidentally-symmetric top free radical and to calculate the six magnetic constants of $N-14O216$. Even if the magnetic quantum numbers of the individual lines were known, secular equations with several sets of real roots would have to be solved, and these roots tested against additional data. Since the quantum numbers are not now known, the calculation is very difficult indeed. The magnetic constants calculated by Lin from the earlier data on $808⟶717$ of $N14O216$ are incompatible with the present data, on $919⟶100,10$. A satisfactory solution has not been obtained, but preliminary calculations indicate that the theory will have to be extended to include corrections for the finite asymmetry of $NO2$, One of us (J.C.B.) is currently working with Lin to accomplish this. This work has been supported by grants from the Research Corporation and the Robert A. Welch Foundation. We wish to acknowledge many helpful conversations with Dr. Chun C. Lin.”