Abstract

H₃⁺ is the simplest polyatomic molecule, and its existence, physical stability, and equilateral triangular structure have been known for many years. However, precise experimental information was lacking until 1980, when infrared spectra were reported for H₃⁺ by Oka and for D₃⁺ by Shy, Farley, Lamb, and Wing. Since that time there have been considerable advances in the spectroscopy of H₃⁺ We have measured extensive spectra of all four isotopes (H₃⁺, H₂D+, D₂H+, D₃⁺) in the 1800–2500-cm⁻¹ region using tunable infrared diode laser sources, a cooled hollow-cathode absorption cell, and a discharge-modulation detection scheme. These data have permitted us to make detailed analyses of the degenerate ν₂ bands of H₃⁺ and D₃⁺, as well as of the Coriolis-coupled ν₂ and ν₃ bands of the mixed isotopes H₂D⁺ and D₂H⁺. The results are summarized and compared, and an extension of the H₃⁺ spectrum to higher values of J is discussed.

© 1986 Optical Society of America