PRECISE MEASUREMENT OF THE PURE ROTATIONAL SUBMILLIMETER-WAVE SPECTRUM OF HCL AND DCL IN THEIR UPSILON = 0, 1 STATES

High-resolution sub-Doppler Lamb-dip measurements were performed on th e low-J pure rotational transitions of the hydrogen chloride isotopome rs (HCl)-Cl-35, (HCl)-Cl-37, (DCl)-Cl-35, and (DCl)-Cl-37 in the submi llimeter-wave region up to 646 GHz. For the J = 1 - 0 transitions of t he two HCl isotopomers, the hyperfine splitting due to the hydrogen nu clear spin-rotation interaction is resolved. Furthermore Doppler-limit ed lines of the DCl J = 3 <-- 2 transition around 965 GKz as well as h yperfine-resolved rotational transitions in the first excited vibratio nal state were recorded up to 1.22 THz. The new frequencies were analy zed in a global fit together with FIR data yielding a set of mass-inva riant rotational parameters. Isotopically invariant hyperfine paramete rs were obtained also from the global fit. Inclusion of the precise re sults from molecular beam electric resonance measurements allowed the determination of higher orders of the vibrational and rotational expan sion coefficients of the chlorine and hydrogen hyperfine interactions. The precise transition frequencies reported here should be useful as secondary calibration standards in the submillimeter-wave and terahert z region. (C) 1998 Academic Press.