The rotational transitions of AuH and AuD with the hyperfine structure due to the gold nucleus (I = 3/2) were observed in the 220, 430, and 650 GHz regions with source modulation microwave spectrometers. The AuH and AuD molecules were generated by sputtering from a gold sheet lining the inner surface of a stainless-steel cathode in a dc glow discharge through hydrogen and deuterium gases, respectively, diluted with argon gas. The nuclear electric quadrupole coupling constant and the nuclear magnetic spin-rotation coupling constant were determined for each isotopomer by a least-squares analysis. (c) 2006 Elsevier B.V. All rights reserved.