Knowledge Bank

The Hamiltonian for a $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi$ state of a diatomic molecule has an indeterminacy between the parameters $\gamma$ and $AD$, which can be removed by a unitary transformation to give either an effective $\gamma ~$ with $A~D=0$ or an effective $A~D$ with $\gamma ~=0.a$ The present work extends this transformation to the magnetic hyperfine and Zeeman terms in the Hamiltonian. Among the hyperfine contributions, the term bI.S is particularly affected by the transformation. Care is therefore required in relating the observed value $b~$ to the electron spin density. Similar considerations apply to observed Zeeman parameters. Applications to the spectra of $NOb$ and $FOc$ will be presented.