Vibrationally excited states of NC4P: millimetre-wave spectroscopy and coupled cluster calculations

Abstract

A fairly efficient method for the production of the unstable NC4P molecule has been found, based on copyrolysis of phosphorus trichloride and cyclopropyl cyanide. This allowed us to extend the study of the rotational spectrum of NC4P to a large number of vibrationally excited states lying between 450 and 750 cm(-1), namely (v(5) v(6) v(7) v(8) v(9)) = (00100), (01000), (10000), (00020), (00101), (01001), (00110), and (01010). The strong Fermi resonance which couples the v(5) = 1 and v(8) = 2 states and the l-type resonances between the different sublevels of the bending states have been taken into account in the analysis of the spectra. The identification of new excited-state spectra was facilitated by CCSD(T) calculations with the cc-pVQZ basis, which provided accurate predictions for a variety of spectroscopic constants, including harmonic vibrational wavenumbers, vibration-rotation coupling constants and l-type doubling constants. Accurate theoretical predictions for the equilibrium structure and the electric dipole moment of NC4P are also presented.