Millimeter-wave spectra of HCCCN

The rotational spectra of cyanoacetylene (HCCCN) were investigated between 148 and 474 GHz. The assignments were obtained on the basis of a global analysis, which uses both vibrational and rotational data available for this molecule. The 876 new experimental frequencies concern 181 vibrational states (up to about 1750 cm(-1)). The global analysis agreement is perfect for states up to 1300 cm(-1) and the fit remains good for higher energy states. High order anharmonic interactions associated with the k(45577) and k(45666) terms of the potential energy, which are not introduced in our model, are responsible for local effects in a few states. The reduced frequencies are plotted for most reported states to illustrate the effects of the numerous interactions. (C) state-by-state fit is also given, but the classical power series in J(J + 1) is not convenient for the heavily perturbed states. (C) 2000 Elsevier Science B.V. All rights reserved

The v(1) band system of H-CC-CN (cyanoacetylene)

The v(1) band system of cyanoacetylene (H-CC-CN) has been observed with an effective resolution of 0.006 cm(-1) v(1) = 3327.37085(3) cm(-1), B-1 = 0.15149762(2) cm(-1), D-1 = 1.8065(3) x 10(-8) cm(-1). Several hot bands from the states v(5) = 1, v(6) = 1, v(7) = 1, 2 (l = 0 and 2), 3 (l = 1 and 3), and 4 (l = 0 and 2), v(6) = v(7) = 1 (l = 0 and 2), and v(6) = 1 and v(7) = 2 (l = 3) have also been observed and analyzed. Many bands show strong local perturbations due to interactions with states which are combinations of the modes 4, 5, 6, and 7. These perturbing states are also described quantitatively, and rovibrational constants are given. (C) 1996 Academic Press, Inc