Investigations of the lowest R-bending vibrations of Ar-DBr (v=0) and Ar-HBr (v=1) are reported using a co-axially configured submillimeter supersonic jet spectrometer. The v = 1 spectra were obtained using glow discharge excitation. Analyses of hyperfine substructure in these spectra provide accurate molecular parameters for Ar-DBr and Ar-BrD isomeric states, direct determination of their corresponding isomerization energies, and respective parameters in the v = 1 HBr stretching vibration of the Ar-HBr isotopomer. This experimental data provides a sensitive probe of the relative energies of potential minima for previously determined 3-D Ar-HBr morphed potential and compared with results from extrapolations to the CCSD(T)/CBS limit. (c) 2008 Elsevier B.V. All rights reserved.