Observation of the infrared absorption spectra of 20NeH+ and 22NeH+ with a difference frequency laser

The fundamental bands of 20NeH+ and 22NeH+ in the region around 3.7 μm have been observed in absorption. The wave numbers of 11 transitions of 20NeH+ and 8 transitions of 22NeH+ have been measured, from which we obtain the following molecular parameters (in cm−1, three standard deviations in parentheses): The equilibrium molecular constants Be, αe, De, βe, ωe, ωeXe, and re have also been derived.