The millimeter wave spectra of NaH and NaD

Utilizing a glow discharge absorption cell, we have detected the v = 0, 1, 2, and 3, J = 0→1 transitions of NaH and the v = 0, 1, 2, and 3, J = 1→2 and v = 0, J = 2→3 transitions of NaD in the millimeter and submillimeter regions of the spectrum. The derived Dunham constants (MHz) are A significant breakdown of the Born–Oppenheimer approximation has been observed.