Vibrational spectra and force constants of symmetric tops: Rovibrational spectra in the ν3 region of monoisotopic species of H 3GeCl, H 3GeBr, and H 3GeI

The gas phase infrared spectra of several monoisotopic species of H ₃GeCl, H ₃GeBr, and H ₃GeI have been recorded in the ν₃ region near 420, 300, and 250 cm ^-1, respectively, with a resolution between 0.03 and 0.04 cm ^-1. Rotational J structure of the fundamental and of several "hot" bands of ν₃ has been resolved and analyzed by means of polynomial methods. The K structure of J clusters is indicated, and α₃^A values were estimated from a band contour simulation. The molecular parameters ν₃⁰, χ₃₃, ( B₃- B₀), and D_J were determined for several isotopic combinations. The ν₃ and 2 ν₃ levels are apparently unperturbed except for H ₃Ge ³⁵Cl species for which Fermi resonance between 2 ν₃ and ν₂ has been established.