THE PURE ROTATIONAL SPECTRUM AND HYPERFINE STRUCTURE OF $HC\ell ^{+}$ STUDIED BY LASER MAGNETIC $RESONANCE^{\ast}$

$^{1}$D. Ray, K.G. Lubic, and R.J. Saykally, Molec, Phys., accepted for publication. $^{\ast}$Supported by NSF Grant #CHE-8007042Pure rotational transitions have been measured for the $HC\ell ^{+}$ molecular ion by the technique of far-infrared laser magnetic resonance spectroscopy. The ions were generated in an intracavity discharge through helium containing a trace of $HC\ell$ at total pressures near 1 Torr. Measurements have been made for the $H^{35}C\ell ^{+}, H^{37}C\ell ^{+}, D^{35}C\ell ^{+}$, and $D^{37}C\ell ^{+}$ isotopes at magnetic flux densities up to 20 kGauss. These spectra are being analyzed according to the $^{2}\Pi$ Hamiltonian of Brown