Rotational transition frequencies of ArD+ were measured with an accuracy of
a few hundred kilohertz in the 0.95-4.7 THz region, using a tunable far-in
frared radiation source. Effective rotational parameters B, D, and H were d
etermined for the ground vibrational state. The observed frequencies were c
ombined with the previous data on all isotopic species of protonated argon
ion to improve the mass-independent Dunham parameters U-kl, Delta(kl)(Ar) a
nd Delta(kl)(H). (C) 1999 Academic Press.