Infrared spectroscopy of 15ND3: The ν2 and ν4 bending fundamental bands

The infrared spectrum of the ammonia isotopologue 15ND3 has been investigated by high resolution Fourier transform spectroscopy in the region from 450 to 1600 cm−1. In total, 2217 transitions involving the (s) and (a) inversion-rotation-vibration levels have been identified and assigned to the ν2 and ν4 bending fundamentals. The assigned transitions have been fitted simultaneously using an inversion-rotation-vibration effective Hamiltonian which includes all symmetry allowed interactions between and within the excited state levels. The adopted model has been successful in rationalizing the complicated energy level pattern. Accurate values for the vibration and rotation spectroscopic constants, including 11 interaction coefficients, have been obtained for both inversion levels of the v2=1 and v4=1 states. The standard deviation of the fit, 0.00071 cm−1, is about two times the estimated measurement precision.

► The high resolution infrared spectrum of ammonia isotopologue 15ND3 is investigated. ► 2217 transitions are identified and assigned to the ν2 and ν4 bending fundamentals. ► They involve the (s) and (a) inversion-rotation-vibration levels of v2=1 and v4=1. ► The assignments have been analysed with an inversion-rotation-vibration Hamiltonian. ► Accurate sets of spectroscopic parameters for both inversion levels are obtained.