Velocity modulation infrared laser spectroscopy of negative ions: The (011)–(001) band of azide (N−3)

We have measured 43 transitions centered at 1972 cm−1 in the (011)–(001) bending hot band of the azide ion (N−3) using diode laser velocity modulation spectroscopy of an NH3/N2O discharge. The data, ranging from P(32) to R(40), were fit to a standard l-type doubling Hamiltonian through quartic terms. The l splittings in the spectrum were unusually large compared with similar molecules. Intensity measurements indicate that the vibrational and rotational degrees of freedom are equilibrated, unlike the case for isoelectronic NCO−. Additional lines of the ν3 fundamental have also been measured, which further refine the values of the ground state parameters.