OH hyperfine ground state: From precision measurement to molecular qubits

Abstract

We perform precision microwave spectroscopy---aided by Stark deceleration---to reveal the low-magnetic-field behavior of OH in its $^{2}\ensuremath{\Pi}_{3∕2}$ rovibronic ground state, identifying two field-insensitive hyperfine transitions suitable as qubits and determining a differential Land\'e $g$ factor of $1.267(5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ between opposite-parity components of the $\ensuremath{\Lambda}$ doublet. The data are successfully modeled with an effective hyperfine Zeeman Hamiltonian, which we use to make a tenfold improvement of the magnetically sensitive, astrophysically important $\ensuremath{\Delta}F=\ifmmode\pm\else\textpm\fi{}1$ satellite-line frequencies, yielding $1\phantom{\rule{0.2em}{0ex}}720\phantom{\rule{0.2em}{0ex}}529\phantom{\rule{0.2em}{0ex}}887(10)\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}$ and $1\phantom{\rule{0.2em}{0ex}}612\phantom{\rule{0.2em}{0ex}}230\phantom{\rule{0.2em}{0ex}}825(15)\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}$.