The CC stretching band ν6 of allene-d4

Abstract The infrared spectrum of C 3 D 4 was measured in the region of the paralled band of the CC stretching vibration ν 6 centered at ν 0 = 1920.2332 cm −1 on a high-resolution Fourier transform spectrometer and deconvolved to a linewidth of ∼ 1 2 of the Doppler width (∼0.0023 cm −1 ). The high resolution reveals the presence of strong perturbations in the K = 4 and K = 8 to 12 levels of the ν 6 upper state. For a quantitative treatment of the observed transitions, a Hamiltonian matrix including six different perturbing states was constructed and used to refine the 6 spectroscopic constants of the ν 6 state and 20 of the constants for the perturbing states. Measurement of the hot band ν 6 + ν 11 − ν 11 whose band center is at 1916.200 cm −1 yielded the anharmonic constant x 6,11 = −4.033 cm −1 .